Low-carbon, high-silicon stainless steel with high-temperature performance for corrosion-resistant containers and manufacturing method

Abstract

The present invention relates to low-carbon, high-silicon, corrosion-resistant stainless steel for high-temperature containers and a manufacturing method. The stainless steel comprises the following components by weight: C: 0.02% to 0.03%, Si: 2.1% to 2.7%, Mn: 0.95% to 1.22%, P ≤ 0.01%, S ≤ 0.001%, Cr: 15.3% to 17%, Ni: 1.1% to 1.9%, Mo: 2.6% to 3.1%, Ta: 0.15% to 0.5%, Ca: 0.0012% to 0.0021%, with the remainder being Fe and unavoidable impurities. Advantages include: the steel plate has excellent strength, toughness, and corrosion resistance, and the addition of Ta ensures the matching of corrosion resistance and toughness. A three-stage heating, staged rolling, straightening, and solution heat treatment method is used to ensure that the finished steel plate has good room-temperature and high-temperature mechanical properties and excellent corrosion resistance throughout the thickness direction.

Description

Technical Field

[0001] The present invention belongs to the field of stainless steel production, and in particular relates to low-carbon, high-silicon, high-temperature performance, corrosion-resistant stainless steel for containers and a manufacturing method thereof. Background Art

[0002] Since its invention in the early 20th century, stainless steel has been widely used for its excellent heat and corrosion resistance, oxidation resistance, ease of fabrication, and surface gloss. Currently, the most widely used stainless steels are categorized as ferritic, austenitic, and martensitic. Ferritic and austenitic grades offer excellent corrosion resistance but relatively low strength. Martensitic aged stainless steels, on the other hand, suffer from relatively poor corrosion resistance, ductility, and weldability. Austenitic stainless steels are exemplified by the 304 and 316 series. The widely used S30403 and S31608 grades, among others, have low room and elevated temperature strength, making them inadequate for high-temperature, high-pressure environments. In particular, after a period of sensitization, these stainless steels fail to meet the required intergranular corrosion resistance. To improve strength, the addition of carbon and niobium has been proposed, but as the carbon content increases, weldability becomes difficult to guarantee.

[0003] In the existing technology, patent publication number CN114192963A discloses a method for preparing a large-area, highly corrosion-resistant, stainless steel-steel explosion composite plate of nuclear power grade. It only proposes a composite process, and does not conduct in-depth research on the performance and application of specific steel plates. In addition, defects are prone to occur at the interface of the composite steel plate, which increases the difficulty of subsequent heat treatment and related preparation processes.

[0004] Patent publication number CN114438408A discloses a low-cost, high-strength, heat-resistant, and corrosion-resistant stainless steel material and a method for producing precision parts using it. The material is composed of the following alloying elements by mass: C: 0-0.03%, O: 0-0.30%, Si: 1.0-2.0%, Mn: 0.2-0.8%, Cr: 12-16%, Ni: 5-10%, Cu: 0.5-2.5%, Mo: 0.5-2.0%, with the balance being Fe. This method combines aging heat treatment with ion nitriding, but this method is costly and unsuitable for large-scale production of components and corresponding steel plates. Patent publication number CN113522972A discloses a process for producing surface-corrosion-resistant stainless steel composite plates, consisting of a stainless steel cladding layer and a carbon steel base layer. The maximum plate thickness studied was only 24 mm, and thicker plates were not studied. Patent publication number CN114075640A discloses a highly corrosion-resistant austenitic stainless steel and its manufacturing method. The stainless steel's chemical composition by weight (wt%) ranges as follows: C: ≤0.020, Si: ≤0.5, Mn: ≤2.0, P: ≤0.025, S: ≤0.010, Ni: 21.5-23.5, Cr: 22.0-24.0, Mo: 5.0-6.0, N: 0.25-0.35, Cu: 0.5-1.5, W: ≤1.0, with the remainder being Fe and unavoidable impurities. This steel has high alloying amounts of Cr, Ni, and Mo, and the addition of W increases production costs and significantly increases manufacturing difficulty. Furthermore, the maximum plate thickness achieved with this method is only 30 mm, and thicker plate has not been studied.

[0005] Therefore, for stainless steel plates for full-thickness pressure vessels (thickness 18-100mm), in order to solve the problems of strength-toughness matching and corrosion resistance under normal temperature and high temperature service environments, it is urgent to develop a new type of corrosion-resistant stainless steel for containers. It is required to have excellent comprehensive performance under normal temperature and high temperature service conditions, and similar or even better corrosion resistance, and the production cost is lower than that of ideal corrosion-resistant stainless steel plates for containers with the same performance materials abroad. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a low-carbon, high-silicon, corrosion-resistant stainless steel for containers with high-temperature performance and a manufacturing method, so as to solve the problems of strength-toughness matching and corrosion resistance of stainless steel plates under normal temperature and high-temperature service environments. The stainless steel for containers with a thickness of 18 to 100 mm has excellent comprehensive performance, good corrosion resistance, and can reduce production costs.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A low-carbon, high-silicon, high-temperature corrosion-resistant stainless steel for containers, comprising the following components by weight:

[0009] C: 0.02% ~ 0.03%, Si: 2.1% ~ 2.7%, Mn: 0.95% ~ 1.22%, P ≤ 0.01%, S ≤ 0.001%, Cr: 15.3% ~ 17%, Ni: 1.1% ~ 1.9%, Mo: 2.6% ~ 3.1%, Ta: 0.15% ~ 0.5%, Ca: 0.0012% ~ 0.0021%, and the rest are Fe and unavoidable impurities.

[0010] The tensile strength of the stainless steel used for the corrosion-resistant container is 550-570 MPa at room temperature, 435-485 MPa at 500°C, 400-465 MPa at 600°C, and 358-415 MPa at 700°C.

[0011] The functions of the above chemical elements are as follows:

[0012] Carbon often forms carbides with other alloying elements in steel, contributing to its strengthening properties. Carbon easily combines with alloying elements to form carbides, causing segregation within the steel and significantly reducing the toughness and ductility of the steel sheet. This invention addresses this issue by adopting a low-carbon design. While maintaining the strength of the steel sheet, the carbon content is controlled to 0.02-0.03%.

[0013] Si has a deoxidizing and desulfurizing effect in steel and can improve the strength of steel plates through solid solution strengthening. Si is also one of the main corrosion-resistant elements. Adding Si to austenitic stainless steel will improve its corrosion resistance in strong oxidizing media. In addition, silicon can also enhance the fluidity of molten steel. Si is an inexpensive alloying element. Adding an appropriate amount of Si to steel can increase the hardness and strength of ferrite in the steel, increase the elastic limit, yield strength and yield ratio, as well as fatigue strength and fatigue ratio of the steel, and improve local corrosion resistance. However, if the Si content is too high, it will have a negative impact on the impact toughness of the heat-affected zone. Therefore, the Si content is limited to 2.1-2.7%.

[0014] Mn is a commonly used desulfurizer in steel. However, excessive Mn addition increases the number of MnS inclusions, increasing the probability of segregation in the steel, resulting in high-strength, low-toughness hard phases of martensite and bainite, which can reduce the weldability of the steel. Therefore, the Mn content should not be too high. Taking into account the strength, toughness, and weldability of the steel plate, the Mn content is set within the range of 0.95-1.22% during composition design.

[0015] S is a brittle element in steel and is also an element that is highly susceptible to segregation, so the lower its content, the better. Both elements also significantly impair the low-temperature toughness of steel. However, considering factors such as steelmaking operability, steelmaking costs, and meeting application requirements, the contents of P and S are controlled below 0.01% and 0.001%, respectively.

[0016] Cr forms various carbides with carbon in steel and dissolves in austenite, providing dispersion, grain refinement, and solid solution strengthening, positively impacting the strength and toughness of the steel. However, excessive addition of Cr can reduce toughness, increase brittleness, and increase production costs. Therefore, the Cr content is controlled within a range of 15.3-17%.

[0017] Ni expands the austenite region while also inhibiting the formation of ferrite in the steel. Combined with Cr, it ensures the steel plate has excellent resistance to oxidation and corrosion. Due to its high cost, the Ni content is limited to 1.1-1.9%.

[0018] Mo increases the probability of austenite formation and refines the austenite structure, improving the strength and toughness of the steel plate. However, Mo negatively impacts the weldability of the steel plate and is a precious metal with a high cost. Therefore, the Mo content in this invention is controlled to 2.6-3.1%.

[0019] Ta can improve the corrosion resistance and toughness matching of steel plates. However, if the content is too high, it will cause the formation of second phase inclusions in the steel plate and increase the production cost. Therefore, the content of Ta is controlled at 0.15% to 0.50%.

[0020] Ca controls the morphology of sulfides in steel, suppressing the formation of MnS by forming CaS. To achieve this effect, the Ca content must be at least 0.0003%. Furthermore, if the Ca content exceeds 0.005%, the resulting CaS becomes excessively large, increasing brittleness and becoming a potential initiation point for fracture cracks. Therefore, the Ca content is limited to 0.0012-0.0021%.

[0021] A method for manufacturing low-carbon, high-silicon, high-temperature performance corrosion-resistant stainless steel for containers, comprising the following processes: smelting - continuous casting - heating - rolling - heat treatment, wherein:

[0022] 1) Heating: The continuous casting billet adopts a three-stage heating method of preheating section - heating section - soaking section;

[0023] The preheating temperature is 915-926°C, and the heating time is 1.6-2.8 min / mm;

[0024] The heating section temperature is 1138-1285°C, and the heating time is 1.7-3.2 min / mm;

[0025] The soaking section temperature is not lower than 1196°C, and the soaking time is not more than 1.6 min / mm;

[0026] 2) Rolling: The continuous casting slab adopts two-stage controlled rolling;

[0027] The finishing rolling temperature of the first stage is 1045-1050℃, and the single-pass reduction rate is not less than 13%;

[0028] The second stage rolling temperature is 935-956℃, with small deformation and rapid rolling, and a single-pass reduction rate of 3%-5%;

[0029] 3) After the steel plate cools to room temperature, it is straightened and the deformation is controlled within 0.5% to 2%;

[0030] 4) Heat treatment: The rolled steel plate is subjected to solution heat treatment;

[0031] The solution temperature is controlled at 1080-1160°C, the net holding time is 0.7-2.1 min / mm, and the steel is water-cooled to room temperature after being taken out of the furnace.

[0032] The continuous casting process includes: a tundish molten steel casting temperature of 1525-1565° C., and adopts electromagnetic stirring or a continuous casting billet soft reduction process.

[0033] In the continuous casting billet soft reduction process, the soft reduction rate is controlled at 8% to 10%.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention provides a simple and reasonable steel plate composition design. By rationally controlling the C and Si contents in the steel, the strength of the steel plate is ensured while also ensuring corrosion resistance. Ca is added to change the shape of inclusions in the steel, making them spherical and smaller in size. To ensure the steel plate possesses excellent strength and toughness, alloying elements Cr, Ni, and Mo are added to the steel to refine the grains and, through precipitation strengthening, ensure good overall performance after solution heat treatment. Ta is added to ensure the matching of the steel plate's corrosion resistance and strength and toughness. This low-carbon, high-silicon stainless steel for corrosion-resistant containers with high-temperature performance has a room-temperature tensile strength of 550-570 MPa, a 500°C tensile strength of 435-485 MPa, a 600°C tensile strength of 400-465 MPa, and a 700°C tensile strength of 358-415 MPa.

[0036] In terms of manufacturing process, the present invention adopts three-stage heating, staged rolling combined with straightening and solution heat treatment to ensure that the finished steel plate has good room temperature and high temperature mechanical properties throughout the thickness direction while also having excellent corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the sensitized intergranular corrosion bending of low carbon, high silicon and high temperature corrosion resistant stainless steel plate for containers Figure 1 .

[0038] Figure 2 It is the sensitized intergranular corrosion bending of low carbon, high silicon and high temperature corrosion resistant stainless steel plate for containers Figure 2 . DETAILED DESCRIPTION

[0039] The present invention will be described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0040] A low-carbon, high-silicon, high-temperature corrosion-resistant stainless steel for containers, comprising the following components by weight:

[0041] C: 0.02% to 0.03%, Si: 2.1% to 2.7%, Mn: 0.95% to 1.22%, P ≤ 0.01%, S ≤ 0.001%, Cr: 15.3% to 17%, Ni: 1.1% to 1.9%, Mo: 2.6% to 3.1%, Ta: 0.15% to 0.5%, Ca: 0.0012% to 0.0021%, and the remainder is Fe and unavoidable impurities. Among them, the volume content of ferrite is not more than 1%.

[0042] The method for manufacturing low-carbon, high-silicon stainless steel plates for corrosion-resistant containers with high-temperature performance comprises the following processes: smelting - continuous casting - heating - rolling - heat treatment, specifically comprising the following steps:

[0043] 1) Using primary furnace smelting, VOD vacuum treatment and other processes for smelting;

[0044] Continuous Casting: The tundish pouring temperature is 1525-1565°C, with low-temperature casting preferred to refine the original cast structure. To control centerline segregation and porosity in the continuous casting slab, electromagnetic stirring or a soft reduction process is used; the soft reduction ratio in this process is controlled at 8%-10%.

[0045] 2) Heating: The continuous casting billet adopts a three-stage heating method of preheating section - heating section - soaking section.

[0046] The preheating section temperature is 915-926°C, and the heating time is 1.6-2.8 min / mm.

[0047] The temperature of the heating section is 1138-1285°C, and the heating time is 1.7-3.2 min / mm; this is to refine the coarse precipitates in the continuous casting billet, ensure the austenitization process of the steel plate, and at the same time ensure the proportion of fine precipitates in the continuous casting billet and avoid the occurrence of excessive grain growth.

[0048] The temperature of the soaking section shall not be lower than 1196°C, and the soaking time shall not exceed 1.6 min / mm.

[0049] 3) Rolling: The continuous casting billet adopts two-stage controlled rolling;

[0050] The finishing rolling temperature in the first stage is 1045-1050℃. In this stage, large deformation is adopted for rapid rolling, and the single-pass reduction rate is not less than 13% to ensure that the recrystallization process near the surface of the steel plate is complete.

[0051] The second stage rolling temperature is 935-956℃, and small deformation is used for rapid rolling. The single-pass reduction rate is 3%-5%, ensuring the stability of the near-surface microstructure of the steel plate.

[0052] 4) After the steel plate is cooled to room temperature, it is straightened, and the deformation is controlled at 0.5% to 2%. Cold straightening further refines the surface grain size of the steel plate, promotes the formation of twins in the surface structure of the steel plate, ensures the complete recrystallization ratio of the steel plate, and thus improves the surface resistance to intergranular corrosion of the steel plate.

[0053] 5) Heat treatment: The rolled steel plate is subjected to solution heat treatment;

[0054] The solution temperature is controlled at 1080-1160°C, the net holding time is 0.7-2.1 min / mm, and the steel is water-cooled to room temperature after being taken out of the furnace.

[0055] Table 1 shows the chemical composition of the example steel, Table 2 shows the continuous casting process of the example steel, Table 3 shows the continuous casting heating process parameters, Table 4 shows the rolling and heat treatment parameters of the example steel, Table 5 shows the room temperature mechanical properties of the example steel plate, Table 6 shows the high temperature mechanical properties of the example steel plate, Table 7 shows the intergranular corrosion results of the steel plate, and Table 8 shows the salt spray test results of the corrosion resistance of the steel plate.

[0056] Table 1 Chemical composition of the examples (wt%)

[0057]

[0058]

[0059] Table 2 Continuous casting process parameters of example steel

[0060] Example Blank thickness / mm Finished product thickness / mm Molten steel casting temperature ℃ Soft reduction of billet % 1 145 19 1564 9 2 145 26 1560 10 3 155 32 1565 8 4 155 51 1563 9 5 200 65 1558 8 6 200 78 1559 10 7 200 82 1561 8 8 200 98 1551 9

[0061] Table 3 Continuous casting slab heating process parameters

[0062]

[0063] Table 4 Rolling and heat treatment process parameters of the example steel

[0064]

[0065]

[0066] Table 5 Mechanical properties of steel plates at room temperature

[0067]

[0068] Table 6 Steel plate high temperature tensile test results

[0069]

[0070] Table 7 Intergranular corrosion results of steel plates

[0071]

[0072] Table 8 Steel plate corrosion resistance salt spray test

[0073]

[0074] The present invention provides a simple and reasonable steel plate composition design. By rationally controlling the C and Si contents in the steel, the strength of the steel plate is ensured while also ensuring corrosion resistance. Ca is added to change the shape of inclusions in the steel, making them spherical and smaller in size. To ensure the steel plate possesses excellent strength and toughness, alloying elements Cr, Ni, and Mo are added to the steel to refine the grains and, through precipitation strengthening, ensure the steel plate possesses excellent overall performance after solution heat treatment. Ta is added to ensure that the steel plate possesses excellent corrosion resistance and a good match between strength and toughness. This low-carbon, high-silicon, corrosion-resistant stainless steel for containers with high-temperature performance has a room-temperature tensile strength of 550-570 MPa, a 500°C tensile strength of 435-485 MPa, a 600°C tensile strength of 400-465 MPa, and a 700°C tensile strength of 358-415 MPa.

Claims

1. A low-carbon, high-silicon, high-temperature corrosion-resistant stainless steel for containers, characterized in that: The following ingredients are included by weight percentage: C: 0.02%~0.03%, Si: 2.1%~2.7%, Mn: 0.95%~1.22%, P≤0.01%, S≤0.001%, Cr: 15.3%~17%, Ni: 1.1%~1.9%, Mo: 2.6%~3.1%, Ta: 0.15%~0.5%, Ca: 0.0012%~0.0021%, the rest are Fe and unavoidable impurities; The tensile strength of the stainless steel used in the corrosion-resistant container is 550~570MPa at room temperature, 435~485MPa at 500℃, 400~465MPa at 600℃, and 358~415MPa at 700℃. The method for manufacturing the low-carbon, high-silicon, high-temperature corrosion-resistant stainless steel for containers comprises the following processes: smelting - continuous casting - heating - rolling - heat treatment, wherein: 1) Heating: The continuous casting billet adopts a three-stage heating method of preheating section - heating section - soaking section; The preheating temperature is 915~926℃, and the heating time is 1.6~2.8min / mm; The heating section temperature is 1138~1285℃, and the heating time is 1.7~3.2min / mm; The soaking section temperature is not lower than 1196°C, and the soaking time is not more than 1.6 min / mm; 2) Rolling: The continuous casting slab adopts two-stage controlled rolling; The finishing rolling temperature of the first stage is 1045~1050℃, and the single-pass reduction rate is not less than 13%; The second stage rolling temperature is 935~956℃, with small deformation and rapid rolling, and the single pass reduction rate is 3%~5%; 3) After the steel plate cools to room temperature, it is straightened and the deformation is controlled within 0.5%~2%; 4) Heat treatment: The rolled steel plate is subjected to solution heat treatment; The solution temperature is controlled at 1080~1160℃, the net holding time is 0.7~2.1min / mm, and the steel is water-cooled to room temperature after being taken out of the furnace.

2. The method for manufacturing a low-carbon, high-silicon, corrosion-resistant stainless steel for a container having high-temperature performance according to claim 1, characterized in that: The process includes the following: smelting - continuous casting - heating - rolling - heat treatment, among which: 1) Heating: The continuous casting billet adopts a three-stage heating method of preheating section - heating section - soaking section; The preheating temperature is 915~926℃, and the heating time is 1.6~2.8min / mm; The heating section temperature is 1138~1285℃, and the heating time is 1.7~3.2min / mm; The soaking section temperature is not lower than 1196°C, and the soaking time is not more than 1.6 min / mm; 2) Rolling: The continuous casting slab adopts two-stage controlled rolling; The finishing rolling temperature of the first stage is 1045~1050℃, and the single-pass reduction rate is not less than 13%; The second stage rolling temperature is 935~956℃, with small deformation and rapid rolling, and the single pass reduction rate is 3%~5%; 3) After the steel plate cools to room temperature, it is straightened and the deformation is controlled within 0.5%~2%; 4) Heat treatment: The rolled steel plate is subjected to solution heat treatment; The solution temperature is controlled at 1080~1160℃, the net holding time is 0.7~2.1min / mm, and the steel is water-cooled to room temperature after being taken out of the furnace.

3. The method for manufacturing a low-carbon, high-silicon, corrosion-resistant stainless steel for use in a container having high-temperature performance according to claim 2, characterized in that: The continuous casting process includes: a tundish molten steel casting temperature of 1525-1565° C., and adopts electromagnetic stirring or a continuous casting billet soft reduction process.

4. The method for manufacturing a low-carbon, high-silicon, corrosion-resistant stainless steel for containers with high-temperature performance according to claim 3, characterized in that: In the continuous casting slab soft reduction process, the soft reduction rate is controlled at 8% to 10%.

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