A hydrogen sulfide corrosion resistant SA516Gr.70 steel plate and a production method thereof

Abstract

The application discloses a kind of anti-hydrogen sulfide corrosion SA516Gr.70 steel plate and production method thereof, belong to steel technical field, the steel plate includes following chemical components: C, Mn, Si, Nb, Ni, Alt, La, Ce;By adding trace lanthanum cerium rare earth alloy instead of alloying, add a small amount of niobium, nickel alloy, obtain-60 ℃ transverse impact reaches 100J above, hardness 130HB~160HB, CEV≤0.41%, with excellent welding performance SA516Gr.70 steel plate, it can keep good mechanical properties after 620±20 ℃ insulation 6 hours simulation after welding, steel plate is no crack by HIC and SSCC inspection.

Description

Technical Field

[0001] This invention belongs to the field of steel technology, specifically relating to an SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion and its production method. Background Technology

[0002] In recent years, with the rapid development of industrial production, the demand for equipment for transporting liquefied petroleum gas (LPG) has increased. Pressure vessels are often used to hold special corrosive substances and are easily corroded, especially when subjected to stress and then further corroded. This can lead to cracks in the steel used in pressure vessels, a phenomenon known as stress corrosion cracking (SCC). Studies have found that the higher the strength or hardness of the steel, the more prone it is to cracking under the influence of hydrogen sulfide (H2S), compromising the material's safe service performance.

[0003] Chinese patent CN118064785A discloses a 355MPa-grade steel plate resistant to hydrogen sulfide corrosion and its production method. The method involves using low-carbon steel with a small amount of chromium, quenching and tempering, or annealing, to meet the -40℃ impact requirement of the steel plate, thus improving its strength and resistance to hydrogen sulfide corrosion. However, this production method suffers from long heat treatment cycles and low production efficiency.

[0004] Chinese patent CN115558756A discloses a method for producing SA516Gr65 steel plates resistant to hydrogen sulfide corrosion. This method involves steel ingots, normalizing, and tempering, resulting in the development of thick steel plates ranging from 165 to 200 mm resistant to hydrogen sulfide corrosion. However, this method requires an additional tempering process and results in a low yield of rolled steel plates from steel ingots.

[0005] Chinese patent CN 108411190 A discloses a thin steel plate resistant to hydrogen sulfide corrosion and its production method. It employs a quenching and tempering process to develop a steel plate with good low-temperature toughness at -30℃, zero banded structure, and a thickness range of 8mm to 20mm, exhibiting excellent resistance to hydrogen sulfide corrosion. However, the quenching and tempering process for this thin steel plate has a long production cycle and a high toughness transition temperature.

[0006] Conventional SA516Gr.70 steel plates have severe banded structure, high hardness, and high ductility transition temperature, which cannot meet the performance requirements of equipment resistant to hydrogen sulfide corrosion. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides an SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion and its production method. By adding trace amounts of lanthanum-cerium rare earth alloys instead of alloying, and adding small amounts of niobium-nickel alloys, an SA516Gr.70 steel plate with a transverse impact strength of over 100J at -60℃, a hardness of 130HB~160HB, and a CEV≤0.41% and excellent weldability is obtained. After simulated welding at 620±20℃ for 6 hours, the steel plate maintains good mechanical properties, and no cracks are found in HIC and SSCC tests.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention provides a hydrogen sulfide corrosion resistant SA516Gr.70 steel plate, which comprises the following chemical composition by weight percentage: C: 0.14~0.17%, Mn: 1.22~1.30%, Si: 0.15~0.35%, P≤0.015%, S≤0.003%, Nb: 0.015~0.020%, Ni: 0.12~0.18%, Alt: 0.020~0.040%, rare earth elements: 0.0020~0.0040%, with the remainder being Fe and unavoidable inclusions; the carbon equivalent of the hydrogen sulfide corrosion resistant SA516Gr.70 steel plate is 0.35-0.41.

[0010] Furthermore, the rare earth element is any one or both of La and Ce.

[0011] The formula for calculating carbon equivalent is: Ceq=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15.

[0012] The metallographic structure of the SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion consists of ferrite and pearlite, with a ferrite volume percentage of 80-85% and a grain size grade of ≥10. This metallographic structure is beneficial for improving the low-temperature toughness of the steel plate.

[0013] The SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion has a tensile strength of 490~530MPa, a yield strength of 325~380MPa, an elongation of ≥25%, a transverse impact absorption energy of KV2 at -60℃ of ≥100J, and a hardness of 130~160HB.

[0014] The present invention also provides a method for producing the aforementioned hydrogen sulfide corrosion resistant SA516Gr.70 steel plate, the method comprising the following steps: converter smelting, LF refining, RH refining, continuous casting, heating, rolling, and heat treatment.

[0015] Furthermore, in the converter smelting step, top and bottom blowing is adopted, requiring P ≤ 0.012% when tapping steel.

[0016] In the LF refining step, the white residue retention time is >20 min, and [S] is controlled to be ≤0.002%.

[0017] In the RH refining step, rare earth alloys are added after calcium treatment, and the calcium content in the steel is ≥0.001%. This is because Ca is a strong deoxidizer in steel, and its deoxidation ability is better than that of rare earths. Calcium treatment first can further remove oxygen from the molten steel, while ensuring that the Ca content in the molten steel is at a high level, allowing it to preferentially combine with oxygen in the molten steel, thus ensuring the effect of rare earths in purifying the molten steel and modifying inclusions. After vacuum circulation, argon soft blowing is performed to promote the flotation of inclusions, and the soft blowing time is ≥15 minutes.

[0018] In the continuous casting step, the molten steel is superheated to 10~30℃, the billet pulling speed is 0.9~1.2m / min, and the billet thickness is 200~300mm; after the continuous casting billet is cut, it is directly transported to the heating furnace for hot charging.

[0019] During the continuous casting process, special protective slag and covering agent are used to protect the molten steel throughout the entire process, and oxidation of the molten steel is strictly prohibited.

[0020] In the heating step, the heating temperature is 1200-1260℃, and the furnace time is (1.0~1.25)×H minutes, where H is the thickness of the steel plate in mm.

[0021] In the rolling process, a two-stage rolling process is adopted, consisting of a recrystallization zone and a non-recrystallization zone. The roughing rolling start temperature is ≥1050℃, the roughing rolling finish temperature is ≥1000℃, and the austenite deformation is 45~50%. The finishing rolling start temperature is ≤860℃, the finishing rolling finish temperature is 780~820℃, the single-pass reduction rate is ≥15%, the cumulative reduction is ≥60%, and the rolling is followed by air cooling.

[0022] In the heat treatment step, the heat treatment method is normalizing; for steel plates with a thickness ≤15mm, the normalizing temperature is 860±10℃, the furnace time is (4~4.5)×H minutes, and the plate is air-cooled after being removed from the furnace; for steel plates with a thickness ≤60mm and a thickness <15mm, the normalizing temperature is 865±10℃, the furnace time is (3.0~3.5)×H minutes, and the plate is air-cooled after being removed from the furnace, with a cooling rate of 1~5℃ / s. Using different normalizing conditions for steel plates of different thicknesses can better reduce banded structures, improve the uniformity of steel plate properties, and improve the steel plate's resistance to hydrogen sulfide corrosion; H is the steel plate thickness in mm.

[0023] In the SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion provided by this invention, the roles of each alloying element and its content in the steel plate are as follows:

[0024] C: Carbon content affects the strength, toughness, and weldability of steel. In this invention, carbon has a strengthening effect on the strength of steel. Too low a carbon content cannot form sufficient carbides and dissolved carbon, resulting in insufficient strengthening phases and hindering the achievement of adequate strength. Simultaneously, excessive carbon affects the impact toughness of steel and deteriorates its weldability. In this invention, the carbon content is controlled between 0.14% and 0.17%.

[0025] Mn: Manganese is an austenite stabilizing element, reducing low-temperature impact toughness while also playing a role in solid solution strengthening. However, excessive manganese can easily lead to segregation, and the banded structure is severely detrimental to the steel plate's resistance to hydrogen sulfide corrosion. In this invention, the manganese content is controlled at 1.22~1.30%.

[0026] Silicon (Si): Silicon can increase the strength of steel, but excessive content can make the steel brittle. Therefore, the silicon content should be controlled between 0.15% and 0.35%.

[0027] P and S: In this invention, P and S are harmful elements and their content should be minimized. Sulfur forms ductile manganese sulfide inclusions with manganese in steel, which elongate along the rolling direction during the rolling process, which is detrimental to the plasticity, toughness, and hydrogen sulfide corrosion resistance of the steel. Phosphorus tends to segregate at grain boundaries, reducing the grain boundaries' resistance to crack propagation and seriously affecting the plasticity and toughness of the steel.

[0028] Niobium (Nb) can combine with carbon and nitrogen to form Nb(C, N), playing a role in precipitation strengthening in steel. Niobium significantly increases the recrystallization temperature of austenite and delays the recrystallization of deformed austenite, which is beneficial for obtaining austenite with a higher degree of deformation. Through appropriate normalizing rolling processes, it can effectively refine the grain structure, improve the strength of the steel, and also improve the low-temperature toughness of the steel. In this invention, the niobium content is controlled at 0.015~0.020%.

[0029] Al: In this invention, aluminum is the main deoxidizing element in the steelmaking process, and it also has the effect of refining grain size. In this invention, the alt content is controlled at 0.020~0.040%.

[0030] La and Ce: Rare earth elements tend to segregate at grain boundaries and other locations, combining with S, metal oxides, silicate impurities, etc. in steel to form high-melting-point spherical compounds. This reduces harmful elements in the steel, purifies grain boundaries, and lowers grain boundary brittleness. Rare earth elements also inhibit excessive grain growth, resulting in smaller grain sizes and improved strength and toughness. In this invention, La+Ce is controlled at 0.0020~0.0040%.

[0031] This invention uses trace amounts of Nb and rare earth elements for alloying without adding other alloying elements. The strength is improved by the grain refinement and precipitation strengthening effects of the trace alloying element Nb, and the low-temperature toughness of the steel is further improved by the purification and modification of inclusions and grain boundaries of the steel by the trace rare earth alloy.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The finished SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion provided by this invention has a low level of inclusions (Class A ≤ 0.5, Class B ≤ 1.0, Class C ≤ 0, and Class D ≤ 0.5), resulting in high purity steel.

[0034] The SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion provided by this invention has a thickness of 6~60mm, tensile strength of 490~530MPa, yield strength of 325~380MPa, elongation ≥25%, transverse impact absorption energy KV2≥100J at -60℃, hardness of 130~160HB, grain size greater than 10 grade, CEV≤0.41%, and excellent weldability. The SA516Gr.70 steel plate, resistant to hydrogen sulfide corrosion, maintains good mechanical properties after being held at 620±20℃ for 6 hours in simulated welding. No cracks were found in the steel plate during HIC and SSCC tests.

[0035] This invention employs a hot-charging heating method for cast billets, eliminating the need for slow cooling and allowing direct feeding into the heating furnace. During rolling, the rolling and normalizing processes are controlled through a normalizing rolling process, resulting in steel plates with excellent strength, toughness, weldability, and corrosion resistance. Compared to traditional heat treatment methods that require the addition of large amounts of alloys and normalizing + tempering or quenching + tempering, this method offers a shorter production cycle, a simpler production process, and significantly reduced costs. Attached Figure Description

[0036] Figure 1 The image shows the metallographic structure of the rolled steel plate in Example 3.

[0037] Figure 2 The image shows the metallographic structure of the steel plate after normalizing in Example 3. It can be seen that the banding is reduced after normalizing, the pearlite distribution is more uniform, and the grains are finer. Detailed Implementation

[0038] This invention provides an SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion. The SA516Gr.70 steel plate comprises the following chemical composition by weight percentage: C: 0.14~0.17%, Mn: 1.22~1.30%, Si: 0.15~0.35%, P≤0.015%, S≤0.003%, Nb: 0.015~0.020%, Ni: 0.12~0.18%, Alt: 0.020~0.040%, rare earth elements: 0.0020~0.0040%, with the remainder being Fe and unavoidable inclusions. The carbon equivalent of the SA516Gr.70 steel plate is 0.35-0.41. The rare earth elements are any one or both of La and Ce.

[0039] The production method of the SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion includes the following steps: converter smelting, LF refining, RH refining, continuous casting, heating, rolling, and normalizing.

[0040] In the converter smelting process, top and bottom blowing is adopted, and P ≤ 0.012% is required when tapping steel.

[0041] In the LF refining process, white slag is used, and the white slag holding time is >20 min. [S] is controlled to be ≤0.002%. After treatment, alloy Nb and nickel plates are added.

[0042] In the RH refining process, the content of harmful gases such as H, O, and N in the steel is reduced, and rare earth alloys are added. Rare earth alloys are added after calcium treatment. After vacuum circulation, argon soft blowing is performed to promote the flotation of inclusions. The soft blowing time is ≥15min.

[0043] During the continuous casting process, special protective slag and covering agent are used to protect the molten steel throughout the process. Oxidation of the molten steel is strictly prohibited. The superheat of the molten steel is 10~30℃, the billet pulling speed is 0.9~1.2m / min, and the billet thickness is 200~300mm. After the continuous casting billet is cut, it is directly transported to the heating furnace for hot charging.

[0044] During the heating process, the heating temperature is 1200-1260℃, and the furnace time is (1.0~1.25)×H minutes, where H is the thickness of the steel plate in mm.

[0045] In the rolling process, a two-stage rolling process is adopted, namely recrystallization zone and non-recrystallization zone. The first stage is austenite recrystallization rolling, i.e. rough rolling, with an initial rolling temperature ≥1050℃, a final rolling temperature ≥1000℃, and a single-pass reduction rate ≥15%. The second stage is austenite non-recrystallization stage, i.e. finish rolling, with an initial rolling temperature ≤860℃, a finish rolling temperature of 780~820℃, a cumulative reduction of ≥60%, and air cooling after rolling.

[0046] During the normalizing process, for steel plates with a thickness ≤15mm, the normalizing temperature is 860±10℃, the furnace time is 4×H minutes, and the plate is air-cooled after being removed from the furnace; for steel plates with a thickness ≤60mm and a thickness <15mm, the normalizing temperature is 865±10℃, the furnace time is 2.2×1.4×H minutes, and the plate is air-cooled after being removed from the furnace, with a cooling rate of 1~5℃ / s; H is the thickness of the steel plate, in mm.

[0047] The present invention will now be described in detail with reference to the embodiments.

[0048] Example 1

[0049] A hydrogen sulfide-resistant SA516Gr.70 steel plate, the chemical composition and weight percentage of which are shown in Example 1 of Table 1, with the remainder being Fe and unavoidable impurities.

[0050] The production method of the aforementioned hydrogen sulfide-resistant SA516Gr.70 steel plate includes the following processes:

[0051] 1) Steelmaking process: The process flow is converter smelting - LF refining - RH refining - continuous casting; the P content of the converter tapping steel is 0.010%; the white slag holding time is 22 minutes, and the S content is 0.002%; the RH treatment vacuum degree is 67MPa, the vacuum holding time is 16 minutes, the H content is 1.3ppm, and rare earth alloys are added after calcium treatment; the continuous casting superheat is 23℃, the casting speed is 1.0m / min, the liquid level fluctuation in the crystallizer is 2mm, and there are no defects on the slab surface.

[0052] 2) Billet heating process: The preheating temperature of the 230mm thick billet is 750-850℃, the first heating section is 1150-1200℃, the second heating section is 1230-1250℃, the soaking temperature is 1220-1240℃, the furnace time is 275 minutes, and rolling is carried out after reaching the temperature.

[0053] 3) Rolling process: Two-stage rolling is adopted. The roughing rolling starts at 1035℃ and ends at a temperature greater than 1000℃. High-temperature, low-speed, and high-reduction rolling is used, with a roll speed ≤2.5m / s and a single-pass reduction rate greater than 16%. The finishing rolling starts at 850℃, with a steel plate thickness of 50mm and ends at 790℃, rolling a thickness of 6mm. After rolling, air cooling is performed.

[0054] 4) Normalizing process: The steel plate is normalized and held at 860℃ for 24 minutes, and then air-cooled after being taken out of the furnace.

[0055] Example 2

[0056] A hydrogen sulfide-resistant SA516Gr.70 steel plate, the chemical composition and weight percentage of which are shown in Example 2 of Table 1, with the remainder being Fe and unavoidable impurities.

[0057] The production method of the aforementioned hydrogen sulfide-resistant SA516Gr.70 steel plate includes the following processes:

[0058] 1) Steelmaking process: The process flow is converter smelting - LF refining - RH refining - continuous casting; the P content of the converter tapping steel is 0.009%; the white slag holding time is 23 minutes, and the S content is 0.002%; the RH treatment vacuum degree is 67MPa, the vacuum holding time is 17 minutes, the H content is 1.2ppm, and rare earth alloys are added after calcium treatment; the continuous casting superheat is 25℃, the casting speed is 1.0m / min, the liquid level fluctuation in the crystallizer is 2mm, and there are no defects on the slab surface.

[0059] 2) Billet heating process: The preheating temperature of the 230mm thick billet is 750-850℃, the first heating section is 1150-1200℃, the second heating section is 1230-1250℃, the soaking temperature is 1220-1240℃, the furnace time is 260 minutes, and rolling is carried out after reaching the temperature.

[0060] 3) Rolling process: Two-stage rolling is adopted. The roughing rolling starts at 1062℃ and ends at a temperature greater than 1000℃. High-temperature, low-speed, and high-reduction rolling is used, with a roll speed ≤2.5m / s and a single-pass reduction rate greater than 15%. The finishing rolling starts at 855℃, with a steel plate thickness of 60mm and ends at 808℃, rolling to 12mm. After rolling, the plate is air-cooled.

[0061] 4) Normalizing process: The steel plate is normalized and held at 865℃ for 48 minutes, then air-cooled after being taken out of the furnace.

[0062] Example 3

[0063] A hydrogen sulfide-resistant SA516Gr.70 steel plate, the chemical composition and weight percentage of which are shown in Example 3 of Table 1, with the remainder being Fe and unavoidable impurities.

[0064] The production method of the aforementioned hydrogen sulfide-resistant SA516Gr.70 steel plate includes the following processes:

[0065] 1) Steelmaking process: The process flow is converter smelting - LF refining - RH refining - continuous casting; the P content of the converter tapping steel is 0.011%; the white slag holding time is 21 minutes, and the S content is 0.001%; ​​the RH treatment vacuum degree is 67MPa, the vacuum holding time is 16 minutes, the H content is 1.1ppm, and rare earth alloys are added after calcium treatment; the continuous casting superheat is 20℃, the casting speed is 1.0m / min, the liquid level fluctuation in the crystallizer is 2mm, and there are no defects on the slab surface.

[0066] 2) Billet heating process: The preheating temperature of the 295mm thick billet is 750-850℃, the first heating section is 1150-1200℃, the second heating section is 1230-1250℃, the soaking temperature is 1220-1240℃, the furnace time is 350 minutes, and rolling is carried out after reaching the temperature.

[0067] 3) Rolling process: Two-stage rolling is adopted. The roughing rolling starts at 1025℃ and ends at a temperature greater than 1000℃. High-temperature, low-speed, and high-reduction rolling is used, with a roll speed ≤2.5m / s and a single-pass reduction rate greater than 16%. The finishing rolling starts at 850℃, with a steel plate thickness of 90mm. The finishing rolling temperature is 805℃, rolled to 30mm, and then air-cooled.

[0068] 4) Normalizing process: The steel plate is normalized and held at 865℃ for 95 minutes in the furnace. After being taken out of the furnace, it is air-cooled at a rate of 2℃ / s.

[0069] Example 4

[0070] A hydrogen sulfide-resistant SA516Gr.70 steel plate, the chemical composition and weight percentage of which are shown in Example 4 of Table 1, with the remainder being Fe and unavoidable impurities.

[0071] The production method of the aforementioned hydrogen sulfide-resistant SA516Gr.70 steel plate includes the following processes:

[0072] 1) Steelmaking process: The process flow is converter smelting - LF refining - RH refining - continuous casting; the P content of the converter tapping steel is 0.010%; the white slag holding time is 21 minutes, and the S content is 0.001%; ​​the RH treatment vacuum degree is 67MPa, the vacuum holding time is 16 minutes, the H content is 1.1ppm, and rare earth alloys are added after calcium treatment; the continuous casting superheat is 20℃, the casting speed is 1.0m / min, the liquid level fluctuation in the crystallizer is 2mm, and there are no defects on the slab surface.

[0073] 2) Billet heating process: The preheating temperature of the 295mm thick billet is 750-850℃, the first heating section is 1150-1200℃, the second heating section is 1230-1250℃, the soaking temperature is 1220-1240℃, the furnace time is 355 minutes, and rolling is carried out after reaching the temperature.

[0074] 3) Rolling process: Two-stage rolling is adopted. The roughing rolling starts at 1025℃ and ends at a temperature greater than 1000℃. High-temperature, low-speed, and high-reduction rolling is used, with a roll speed ≤2.5m / s and a single-pass reduction rate greater than 17%. The finishing rolling starts at 860℃, with a steel plate thickness of 150mm and ends at 796℃, rolling to 60mm. After rolling, the plate is air-cooled.

[0075] 4) Normalizing process: The steel plate is normalized and held at 865℃ for 185 minutes in the furnace, and then air-cooled after being taken out of the furnace at a cooling rate of 4℃ / s.

[0076] Comparative Example 1

[0077] The rest is the same as in Example 1, except that La+Ce in the ingredients are omitted.

[0078] Comparative Example 2

[0079] The rest is the same as in Example 4, except that the normalizing process is as follows: the steel plate is normalized and held at 860°C for 24 minutes, and then air-cooled after being taken out of the furnace.

[0080] Table 1

[0081]

[0082] The properties of the SA516Gr.70 steel plates in the above embodiments and comparative examples are shown in Table 2 below.

[0083] Table 2

[0084]

[0085] The metallographic structure and inclusion analysis results of the SA516Gr.70 steel plates in the above embodiments and comparative examples are shown in Table 3 below.

[0086] Table 3

[0087]

[0088] The mechanical properties of the SA516Gr.70 steel plates in the above embodiments and comparative examples after being simulated by welding at 620℃ for 6 hours are shown in Table 4.

[0089] Table 4

[0090]

[0091] According to standard GB / T4157-2006 "Metals in Hydrogen Sulfide Environment - Laboratory Tests for Resistance to Special Forms of Environmental Cracking", a four-point bending test was conducted at room temperature and pressure. The test used a four-point bending specimen according to GB / T 15970.2-2000. The test solution was solution A, the applied stress was SMYS / 1.5 (SMYS=420MPa), and the test time was 720h. The SA516Gr.70 steel plates in each example and comparative example were subjected to HIC and SSCC tests and hardness values. The results are shown in Table 5.

[0092] Table 5

[0093]

[0094] As can be seen from the above, the steel plate provided by the present invention meets the following performance requirements: tensile strength Rm: 490-530MPa, yield strength Rel: 325-380MPa, elongation A (L0=50mm) ≥22%, average transverse V-shaped impact at -60℃ ≥100J, hardness 130~160HB, grain size greater than grade 8, good mechanical properties after simulating welding at 620±20℃ for 6 hours, resistance to hydrogen sulfide corrosion, and fine and uniform grain size, which is beneficial to the strength and toughness of the steel plate.

[0095] This invention controls the content of oxygen, sulfur, and other non-metallic inclusions in steel by adding rare earth alloys. At the same time, it allows the inclusions remaining in the steel to combine with rare earths, changing their morphology into fine spherical inclusions. This reduces the stress around the inclusions. Under hydrogen sulfide corrosion environment and fatigue stress conditions, the steel plate showed no cracks in HIC and SSCC tests, thus improving the safety and lifespan of the product.

[0096] The above detailed description of an SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion and its production method, with reference to the embodiments, is illustrative rather than limiting. Several embodiments can be listed within the defined scope. Therefore, variations and modifications without departing from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A hydrogen sulfide corrosion resistant SA516Gr.70 steel plate, characterized in that, The hydrogen sulfide-resistant SA516Gr.70 steel plate comprises the following chemical composition by weight percentage: C: 0.14~0.17%, Mn: 1.22~1.30%, Si: 0.15~0.35%, P≤0.015%, S≤0.003%, Nb: 0.015~0.020%, Ni: 0.12~0.18%, Alt: 0.020~0.040%, rare earth elements: 0.0020~0.0040%, with the remainder being Fe and unavoidable inclusions; the carbon equivalent of the hydrogen sulfide-resistant SA516Gr.70 steel plate is 0.35-0.

41. The metallographic structure of the SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion is ferrite and pearlite, with a grain size grade ≥10; its tensile strength is 490~530MPa, yield strength is 325~380MPa, elongation is ≥25%, transverse impact absorption energy at -60℃ KV2≥100J, and hardness is 130~160HB; no cracks were found after HIC and SSCC tests.

2. The SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion according to claim 1, characterized in that, The rare earth element is any one or both of La and Ce.

3. A method for producing SA516Gr.70 steel plate resistant to hydrogen sulfide corrosion as described in claim 1 or 2, characterized in that, The production method includes the following steps: converter smelting, LF refining, RH refining, continuous casting, heating, rolling, and heat treatment.

4. The production method according to claim 3, characterized in that, In the RH refining step, rare earth alloys are added after the calcium treatment is completed.

5. The production method according to claim 3, characterized in that, In the continuous casting step, the molten steel is superheated to 10~30℃, the billet pulling speed is 0.9~1.2m / min, and the billet thickness is 200~300mm.

6. The production method according to claim 3, characterized in that, In the heating step, the soaking temperature is 1200-1260℃, and the furnace time is (1.0~1.25)×H minutes, where H is the thickness of the steel plate in mm.

7. The production method according to claim 3, characterized in that, In the rolling process, the roughing rolling start temperature is ≥1050℃, the roughing rolling finish temperature is ≥1000℃, and the single-pass reduction rate is ≥15%; the finishing rolling start temperature is ≤860℃, the finishing rolling finish temperature is 780~820℃, the cumulative reduction is ≥60%, and the rolling is followed by air cooling.

8. The production method according to claim 3, characterized in that, In the heat treatment step, the heat treatment method is normalizing; for steel plates with a thickness ≤15mm, the normalizing temperature is 860±10℃, the furnace time is 4×H minutes, and the plate is air-cooled after being normalized; for steel plates with a thickness ≤60mm and a thickness <15mm, the normalizing temperature is 865±10℃, the furnace time is 2.2×1.4×H minutes, and the plate is air-cooled after being normalized, with a cooling rate of 1~5℃ / s; H is the thickness of the steel plate, in mm.

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