DE112021006024T5 - A PRESSURE VESSEL STEEL PLATE WITH A THICKNESS EXCEEDING 200 TO 250 MM AND HAVING RESISTANCE TO HYDROGEN INDUCED CRACKING, AND METHOD OF MANUFACTURE THEREOF - Google Patents

Abstract

The invention relates to a pressure vessel steel plate with a thickness of more than 200 to 250 mm and with resistance to hydrogen-induced cracking, the chemical composition of the steel plate in percentage by weight being: C: 0.10-0.20%, Si: 0, 15-0.40%, Mn: 0.95-1.35%, P: ≤0.005%, S: ≤0.0008%, Cr: 0.10-0.30%, Ni: 0.25-0 .40%, Mo: 0.08-0.12%, Old: 0.02-0.05%, Nb: 0.01-0.02%, V: 0.01-0.03%, Ti: 0.01 - 0.02%, B: ≤ 0.0005%, the balance is Fe and unavoidable impurity elements. At the same time, the chemical composition of the steel plate corresponds to the carbon equivalent Ceq≤0.45%, where Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15. By strictly controlling the purity of the molten steel, the metallurgical quality of the continuous cast billet, and the application of high-temperature diffusion heating, high penetration rolling and heat treatment processes such as normalizing + water-accelerated cooling + tempering, the invention realizes the optimal matching of the mechanical properties of the pressure vessel steel plate with large thickness and with resistance to hydrogen-induced cracking, and greatly improves the internal quality and resistance to hydrogen-induced cracking of the steel plate.

Description

technical field

The invention relates to a pressure vessel steel plate with a thickness of more than 200 to 250 mm and with resistance to hydrogen induced cracking and manufacturing methods therefor, in particular to an extra thick steel plate resistant to hydrogen induced cracking and suitable for the manufacture of plate-welded pressure vessels and can be used in a wet hydrogen sulfide environment and methods of manufacture therefor. The invention belongs to the technical field of production of iron-based alloys.

State of the art

There are two main methods for manufacturing thick-walled pressure vessels: forge welding and plate welding. In comparison, plate welding has advantages such as short manufacturing cycle, relatively low cost, easy material sourcing and smooth plate performance. Therefore, replacing forge welding with plate welding is the long-term development direction of the pressure vessel industry in the future. In the manufacture of pressure vessels, the thick-walled plate-welded structure is more difficult to manufacture than the forge-welded structure. There are two main factors limiting the commercial development of plate welded pressure vessels. One is that the container manufacturing plant is limited by the capacity of the pipe section forming equipment. The other is that the physical quality level and stability of extra-thick steel plate are poor, which cannot fully meet the manufacturing requirements of thick-walled containers.

In the 1990s, pressure vessels with a wall thickness of more than 150 mm were mostly manufactured by forge welding. In recent years, with the large-scale petrochemical plants and the rapid development of the petrochemical industry, the demand for pressure vessels with a wall thickness of more than 150mm has been increasing rapidly, and the production capacity of large forgings could not meet the market, so it is imperative to Replacing forgings with thick steel plates is imminent. With the improvement of melting technology and rolling capacity, and with mastering the heat treatment performance of materials, the physical quality level of extra thick steel plate for pressure vessels has been greatly improved, and pressure vessel manufacturers have also accumulated richer experience in the production of large thickness plate welded vessels, especially received a number of practical and mature technologies in the formation of thick-walled pipe joints. The advancement of extra thick steel plate manufacturing technology and plate weld mold technology have made great strides in enlarging plate welded pressure vessels. At present, the maximum wall thickness of plate welded pressure vessels has reached 200mm. Pressure vessels with a wall thickness of more than 200mm are fully plate weldable formable, but the technical bottleneck around the physical quality level and stability of extra thick steel plate for pressure vessels is not yet broken, which is not enough to fully meet the current heavy-wall vessel manufacturing requirements . In particular, the extra thick steel plates for pressure vessels used in corrosive environments with wet hydrogen sulfide at low temperatures require not only good internal quality, good welding performance and well-matched mechanical properties, but also excellent resistance to hydrogen-induced cracking in order to maintain the Ensuring device security for efficient operation. Therefore, it is extremely difficult to manufacture.

(1) Currently, SA516Gr70 (HIC) has been publicly reported as the thickest domestic anti-hydrogen cracking steel plate in China, with a maximum thickness of 200mm. Steel sheets for pressure vessels, which are resistant to hydrogen-induced cracking and have a thickness of more than 200mm, still depend on imports. There are fewer patents for heavy gauge pressure vessel steels with resistance to hydrogen induced cracking for use in wet hydrogen sulfide environments. The document with the publication number CN10108330398A refers to a "Extra Thick Acid-Resistant Vessel Plate Manufacturing Process" that provides a pressure vessel steel plate with resistance to hydrogen-induced cracking that is fabricated from steel ingots. The Cr, Ni and Cu multi-alloy design and subsequent normalizing heat treatment achieves reasonable performance, but the maximum thickness of the steel plate is only 200mm, and in the performance specification, the impact temperature is only -20℃. Error detection meets Class I requirements, but the error detection standard is not specified. Therefore, the scope is small. The document with the publication number CN111349859A refers to "a kind of composite rolled 500 MPa Z-laminated steel sheet for containers and its manufacturing method". It provides extra-thick, low-temperature tank steel plate manufactured by composite slab. Method of assembling is that two blanks are connected. The combined construction of Nb and V micro-alloys and the subsequent normalizing heat treatment achieves reasonable performance, but the maximum thickness of the steel plate is 210mm. In the specification of performance, the defect detection corresponds to the standard NB/T47013.3 Level I, but the resistance to hydrogen induced cracking is not mentioned. The document with the publication number CN109355579A refers to a type of "12Cr2Mo1VR extra thick steel plate for high temperature pressure vessels and their manufacturing process". It is an extra-thick steel plate for high-temperature pressure vessels, made by water-cooled die-casting of steel ingots. Appropriate performance is achieved by appropriate composition design and then quenching twice + tempering heat treatment twice. However, the maximum thickness of the steel plate is 300mm, and in the specifications, the inner quality of the steel plate is poor, and the flaw detection can only meet the level III of the JB/T47013 standard, without mentioning the resistance to hydrogen-induced cracking, so the requirements as cannot meet the replacement of forgings and is not applicable in corrosive environments with wet hydrogen sulfide. The document with the publication number CN108754321B refers to a type of "extra-thick, normalized, high-strength, pressure vessel steel plate and its manufacturing process". It provides an extra-thick, normalized, high-strength pressure vessel steel plate manufactured by composite slab. Method of assembling is that three blanks are connected. Adequate properties can be achieved by compositional design of the Ni and Cu alloy combination and subsequent normalizing heat treatment. The maximum thickness of the steel plate is 250 mm. In the performance specification, the impact temperature is only 0°C and the fault detection can only meet Level I of the JB/T47013 standard. Resistance to hydrogen induced cracking is not mentioned, so it is not suitable for use in corrosive environments with wet hydrogen sulfide at low temperatures.

content of the invention

The technical problem to be solved by the present invention is to provide a hydrogen-induced cracking resistant pressure vessel steel and its manufacturing method in view of the above prior art. The steel plate has a thickness of more than 200-250mm, and after a simulated high-temperature and long-term post-weld heat treatment, it still has well-matched mechanical properties and excellent resistance to hydrogen-induced cracking, making it suitable for use in a wet environment Hydrogen sulfide is suitable and can fully meet the requirements for manufacturing thick-walled pressure vessels by plate welding.

The technical solution that the invention applies to solve the above problems is: a steel plate for pressure vessels with a thickness of more than 200-250 mm and with resistance to hydrogen-induced cracking, the chemical composition of the steel plate in percent by weight is: C: 0 ,10-0.20%, Si: 0.15-0.40%, Mn: 0.95-1.35%, P: ≤0.005%, S: ≤0.0008%, Cr: 0.10- 0.30%, Ni: 0.25-0.40%, Mo: 0.08-0.12%, Alt: 0.02-0.05%, Nb: 0.01-0.02%, V : 0.01-0.03%, Ti: 0.01-0.02%, B: ≤0.0005%, the balance is Fe and unavoidable impurity elements. At the same time, the chemical composition must correspond to the carbon equivalent Ceq≤0.45%, where Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15.

• C kann die Festigkeit der Stahlplatte erheblich verbessern, aber mit zunehmendem Kohlenstoffgehalt nimmt die Zähigkeit der Stahlplatte ab und besteht die Gefahr einer Karbidentmischung, dadurch unterscheidet sich die Härte der Entmischungszone von der des umgebenden Gewebes, was zu einer wasserstoffinduzierten Risskorrosion führt.

The steel plate for pressure vessels with well-matched comprehensive mechanical properties and excellent resistance to hydrogen-induced cracking in the invention belongs to iron-based alloys. The main chemical elements in steel and their functions are as follows:

• C can greatly improve the strength of the steel plate, but as the carbon content increases, the toughness of the steel plate decreases and there is a risk of carbide segregation, thereby making the hardness of the segregation zone different from that of the surrounding tissue, resulting in hydrogen-induced crevice corrosion.

Considering the strength, toughness and resistance to hydrogen-induced cracking of the steel plate in full, the C content is set to 0.10-0.20% in the invention.

Mn improves the strength of steel through solid solution strengthening. However, if more than 1.05% Mn is added, the susceptibility to hydrogen-induced cracking increases, so the Mn content should not be too high. Considering the steel plate strength and the resistance to hydrogen-induced cracking in full, the Mn content is set at 0.95-1.35% in the invention.

Si is mainly used as a reducing agent and deoxidizing agent in steelmaking and has some effect on solid solution strengthening. At the same time, Si elements are easily separated at the grain boundary, which promotes the formation of intergranular cracks. In addition, if the Si content is too high, the hardness of the weld and the heat-affected zone cannot be controlled. Therefore, the Si content is set to 0.15-0.40% in the invention.

Cr is an element that improves hardenability and can greatly increase the strength of steel. However, when the content is too high, the brittleness transition temperature increases. In the invention, the Cr content is controlled in the range of 0.10-0.30%.

Ni mainly plays the role of solid solution strengthening in steel and can improve toughness at the same time. However, too much Ni content increases the cost significantly, so its use should be limited. In the invention, the Ni content is controlled in the range of 0.25-0.40%.

Mo is an element that improves hardenability and can greatly increase the strength of steel. In the invention, the Mo content is controlled in the range of 0.08-0.12%.

Old: Aluminum is mainly used for deoxidation and grain refinement. In the invention, the Al content is controlled to 0.02-0.05%.

Nb: Niobium can greatly increase the austenite recrystallization temperature of steel, expand the recrystallization zone range, and facilitate high-temperature rolling. Niobium can also inhibit the growth of austenite grains and have the function of fine grain strengthening and precipitation strengthening. In the invention, the Nb content is controlled to 0.01-0.02%.

V and Ti form carbonitrides with elements C and N, which can retard austenite recrystallization and refine ferrite grains, while improving the strength and toughness of steel plate. In the invention, the V content is controlled to 0.010 - 0.03% and the Ti content to 0.010 - 0.02%.

P and S are harmful elements. With the increase of the S content in the steel, the content of MnS and FeS also increases, leading to local loosening of the microstructure and an increased susceptibility to hydrogen-induced cracking. When the P content is very low, cracks may appear on MnS, but the size is too small to detect. If the P content is high (e.g. P=0.4%), even if S is very low (S=0.001%), the cracks may also be generated at oxide inclusions and grain boundaries and propagate. Therefore, in the invention, the S content is set to ≦0.0008% and the P content to ≦0.005%.

The steel plate product of the invention is manufactured by composite slab, and the main process steps are sequentially: melting and casting of continuous cast ingots, manufacturing of composite slab by vacuum welding and assembly, rolling of composite slab to form, rolling into finished steel plate, and heat treatment. The specific operations are as follows:

(1) Melting and casting of continuous cast ingots

The continuously cast slabs produced by the same melting furnace and having the same size with a 450 mm thick section serve as the composite slab blanks.

(2) The melting process of pure steel is used in the production of the continuous cast ingots. Some measures such as using a large tundish in casting and increasing the argon soft blowing time can completely float the nonmetallic inclusions into the slag, thereby reducing the nonmetallic inclusion content of the steel and improving the purity of the molten steel. The non-metallic inclusions of type A, type B, type C and type D in the molten steel are controlled so that the index of each type of inclusions is ≦1.0 and their sum is ≦2.5. With low superheat, argon protection casting processes and dynamic soft reduction technology, the continuously cast billets are controlled in such a way that segregation of type C has an index below 1.0 and the porosity has an index below 0.5. After the continuous cast ingots leave the assembly line, they are covered and slowly cooled for ≥72 hours to fully diffuse the hydrogen;

In addition, the production process of continuous cast ingots is: KR pretreatment → converter smelting → LF refining → RH refining → continuous casting. After the converter melting, a slag removal treatment is performed. After the RH vacuum is broken, the soft argon blowing takes more than 30 minutes. In the continuous casting process, the degree of overheating of the molten steel is 10 to 30 °C.

(2) Manufacture of composite slab by vacuum welding and assembly

A surface of the continuously cast billet is milled and assembled by electron beam welding in a vacuum chamber, and the billet assembling method is that two billets are joined. The composite slab is manufactured using a conventional method that has been disclosed, and the thickness of the composite slab obtained is 860-870 mm.

Rolling the composite slab to form

The composite slab is heated in a holding furnace. While the ingot segregation is fully diffused, the partial metallurgical bonding of the composite interface is completed by high temperature diffusion. In the roughing mill, the single-stand rolling process with high penetration is adopted, and the rolling passes are appropriately distributed. Through repeated recrystallization, the bonded interface achieves a strong metallurgical bond. The thickness of the intermediate slab is adjusted to 400-450 mm. After the intermediate slabs leave the assembly line after rolling, they are placed in a cover and slowly cooled for ≥72 hours to fully diffuse the hydrogen.

In addition, the composite slab can be subjected to a segmented heating process. The steel is stressed below 550°C and the steel is held for 1 to 2 hours. In the low temperature range, the temperature is raised to 820 ± 20 °C at a rate not exceeding 75 °C/h and held for 3 to 5 hours. In the medium-temperature range, the temperature is raised to 1000 ± 20 °C at a rate not exceeding 110 °C/h and held for 2 hours; in the high temperature range, the temperature is increased to 1220-1250 °C and maintained for 8 to 12 hours.

In addition, the main task of forming the composite slab is to complete the rolling and joining in the roughing mill and obtain an intermediate slab of reasonable size. The starting rolling temperature is 1060-1100°C and the finishing rolling temperature is 950-980°C. A high penetration rolling process is used. There are at least 4 rolling passes in longitudinal rolling, with the reduction in each individual pass being ≥50mm. After the steel plate leaves the assembly line, it is covered and slowly cooled for ≥72 hours.

Rolling into the finished steel plate

After slow cooling and finishing, the intermediate slab is reheated in a step-by-step heating furnace to make it fully austenitized. The second high-temperature diffusion heating further reduces the segregation defects in the core of the slab and at the same time provides favorable conditions for the realization of the second high-penetration rolling. In addition, the intermediate slab can be heated in stages. The total heating time is 620 minutes, the second stage heating temperature is 1200-1250℃, the soaking stage temperature is 1180-1250℃, the sum of the second stage heating time and the soaking stage heating time is ≥270 minutes to ensure sufficient Ensure diffusion of segregations.

Rolling is divided into two stages: rough rolling and finish rolling. The rolling deformation is mainly concentrated in the rough rolling stage, which adopts the high penetration rolling process. There are at least 2 rolling passes with the reduction in each individual pass being ≥50mm. The main task of finish rolling is to precisely control the thickness tolerance and keep a good shape. The start rolling temperature of finish rolling is 820 ± 20 °C. The thickness of the serviceable steel plate is the thickness of the finished steel plate plus 30mm. In other words, in the finishing roll phase, the total rolling deformation of the steel plate in the thickness direction is 30 mm. After the steel plate leaves the assembly line, they are stacked and slowly cooled, and slowly cooled for ≥48 hours to fully diffuse the hydrogen.

(4) Heat treatment: The steel plate is successively normalized and tempered. After normalization, water in the water tank is used to speed up cooling.

In addition, the heating temperature can be 880-910 °C when normalizing, and the holding time coefficient: 2.0-2.5 min/mm. After leaving the furnace, the steel plate is cooled with water to cool the surface of the steel plate to 400-500°C. In order to prevent the strength of the steel plate after the post-weld simulated heat treatment from greatly decreasing, the tempering temperature of the steel plate of the invention is not lower than the post-weld simulated heat treatment temperature. When tempering: tempering temperature 610-630 °C, holding time coefficient: 3.5-4.5 min/mm.

The main technical difficulty of pressure vessel steel plates with large thickness and resistance to hydrogen-induced cracking, especially as a substitute for forged products, is mainly reflected in the fact that due to the limitation of the metallurgical quality of the billets themselves and the capacity of the rolling mill, it is difficult to determine the internal quality, durability to ensure against hydrogen induced cracking and the mechanical properties of the core of steel plates.

• (1) Die Verbundbramme wird verwendet, um den Stahlbarren zu ersetzen, und die Methode zur Montage besteht darin, zwei Basisbrammen zusammenzusetzen.
• (2) Durch einige Maßnahmen, z.B. die Reduzierung des Gehalts an leicht entmischbaren Elementen wie C, Mn, S, P usw., die Reduzierung der Überhitzung von Strangguss-Stahlschmelze und die Einführung einer dynamischen Soft-Reduktion usw., werden die metallurgischen Defekte der Stranggussrohlinge wie Entmischung und Porosität gemildert werden. Die Entmischung von Typ C der Stranggussrohlinge weist einen Index unter 1,0 auf und die Porosität einen Index unter 0,5. Nachdem der Stranggussrohlinge das Fließband verlassen haben, werden sie abgedeckt und ≥72 Stunden lang langsam abgekühlt, um den Wasserstoff vollständig zu diffundieren. In der Erfindung beträgt der Überhitzungsgrad der Stahlschmelze beim Strangguss 10 bis 30 °C.
• (3) Durch einige Maßnahmen z.B. die Verwendung eines großen Zwischenbehälters zum Gießen und die Verlängerung der Zeit des sanften Einblasens von Argon können die nichtmetallischen Einschlüsse vollständig in die Schlacke aufschwimmen, wodurch der Gehalt an nichtmetallischen Einschlüssen im Stahl verringert und die Reinheit der Stahlschmelze verbessert wird. Nichtmetallische Einschlüsse vom Typ A, Typ B, Typ C und Typ D in der Stahlschmelze werden so gesteuert, dass der Index des einzelnen Typs von Einschlüssen ≤ 1,0 und ihre Summe ≤ 2,5. In der Erfindung dauert das sanfte Einblasen von Argon mehr als 30 Minuten.
• (4) Verwendet wird ein solches Stahlwalzverfahren, wobei die Bramme zuerst geformt und dann gewalzt wird, und durch zwei Wärmebehandlungen gefertigt wird. Durch zwei Hochtemperatur-Diffusionserwärmungen und hoher Durchdringungswalzprozesse werden die Entmischungen vollständig diffundiert und die losen Fehlstellen zusammengepresst.
• Der folgende Prozess wird angewendet: Normalisierung + wasserbeschleunigte Abkühlung + Anlasswärmebehandlung. Durch die Regulierung der Mikrostruktur wird die metallografische Struktur gleichmäßiger und feiner und die mechanischen Eigenschaften und die Beständigkeit gegen wasserstoffinduzierte Rissbildung des Kerns werden verbessert.

In order to solve the above problems, the invention has taken appropriate technological measures regarding the manufacturing process of the product, in particular as follows:

• (1) The composite slab is used to replace the steel ingot, and the method of assembling is to put two base slabs together.
• (2) By taking some measures, such as reducing the content of easily segregated elements such as C, Mn, S, P, etc., reducing the superheat of continuously cast molten steel, and introducing dynamic soft reduction, etc., the metallurgical defects are eliminated of the continuously cast billets such as segregation and porosity are reduced. The segregation of type C ingots has an index below 1.0 and the porosity index below 0.5. After the continuous cast ingots leave the assembly line, they are covered and slowly cooled for ≥72 hours to fully diffuse the hydrogen. In the invention, the degree of superheat of the molten steel in continuous casting is 10 to 30°C.
• (3) By taking some measures such as using a large tundish for casting and increasing the time of soft argon blowing, the nonmetallic inclusions can be completely floated into the slag, thereby reducing the nonmetallic inclusion content of the steel and improving the purity of the molten steel . Type A, type B, type C and type D non-metallic inclusions in the molten steel are controlled so that the index of each type of inclusions ≤ 1.0 and their sum ≤ 2.5. In the invention, the argon soft blowing takes more than 30 minutes.
• (4) Such a steel rolling method is used, in which the slab is first formed and then rolled, and is finished by two heat treatments. With two high-temperature diffusion heating processes and high penetration rolling processes, the segregations are completely diffused and the loose imperfections are pressed together.
• The following process is applied: normalization + water accelerated cooling + tempering heat treatment. By regulating the microstructure, the metallographic structure becomes more uniform and fine, and the mechanical properties and resistance to hydrogen-induced cracking of the core are improved.

• Da die Stranggussrohling während des Erstarrungsprozesses schneller abkühlt, ist ihre innere Qualität deutlich besser als die von herkömmlichen Stahlbarren. Die Erfindung verwendet die Verbundbramme als Bramme, was nicht nur das Problem eines unzureichenden Kompressionsverhältnisses bei der Herstellung einzelner Bramme im Stranggussverfahren löst, sondern auch auch die praktischen Probleme von schwerwiegenden metallurgischen Defekte wie Entmischung und Porosität im Kern des Stahlbarrens löst.

The principles on which the invention adopts the above process measures and scope of process parameters are as follows:

• Since the continuous cast billet cools faster during the solidification process, its internal quality is significantly better than that of conventional steel billets. The invention uses the composite slab as the slab, which not only solves the problem of insufficient compression ratio in the production of individual slabs in the continuous casting process, but also solves the practical problems of serious metallurgical defects such as segregation and porosity in the core of the steel ingot.

The purpose of applying the method of assembling the two slabs is to avoid metallurgical defects at the 1/2 position of the thickness of the continuous cast ingot in the core of the steel plate, so as to improve the performance of the core of the steel plate. Compared to the method of manufacturing with single continuously cast slab, there are the following disadvantages: The upper or lower 1/4 position in the thickness direction of the steel plate assembled by two slabs is exactly half of the thickness of the continuously cast ingot. This is also the position where metallurgical defects such as segregation and porosity are concentrated, and the position number has been changed from one to two. However, the location of metallurgical defects such as segregation and porosity is relatively shifted outward in the thickness direction, closer to the top and bottom of the composite slab, favoring the diffusion of segregation in high-temperature heating and the lamination of loose defects in high-penetration rolling. Since the metallurgical defects such as segregation and porosity are unavoidable, the invention controlled the segregation index of type C to below 1.0 and the porosity defect to below 0.5 by some measures such as reducing the content of easily segregated elements such as C , Mn, S and P, the reduction of superheating of continuously cast steel melts and the introduction of dynamic soft reduction, etc. In this way, the metallurgical quality, mechanical properties and resistance to hydrogen-induced cracking at the upper or lower 1/4 - Position of the steel plate guaranteed.

Nonmetallic inclusions are hydrogen traps. When hydrogen enters the steel, it accumulates at the inclusion interface and forms hydrogen molecules. When the hydrogen pressure exceeds the strength limit of the material, hydrogen-induced cracking occurs in the inhomogeneous structure. The invention uses some measures such as using a large tundish for casting and lengthening the time of gently blowing argon so that the nonmetallic inclusions are completely floated in the slag. Type A, type B, type C and type D non-metallic inclusions in the molten steel are controlled so that the index of each type of inclusion is ≦1.0 and their sum is ≦2.5. Controlling the content, size and shape of non-metallic inclusions reduces the susceptibility of pressure vessel steel plates to hydrogen induced cracking and thereby improves the resistance to hydrogen induced cracking.

Limited by the capacity of the rolling mill, it is difficult for the rolling force to penetrate the core of the steel plate during rolling. The traditional rolling process cannot guarantee the inner quality and core performance of the steel plate. In time, due to the large thickness of the steel plate, the effect of grain refinement from the controlled rolling process and the controlled cooling process is not good. Even under normalizing process conditions, the steel plate grains are still relatively coarse due to the low cooling rate in air. The strength, low-temperature impact resistance, resistance to hydrogen-induced cracking and stability of the steel plate are difficult to meet the design requirements. In order to ensure that the extra thick steel plate has the quality performance of forging with the same thickness, and fully meet the requirements of the manufacturing process in which forge welding is replaced by plate welding, the present invention adopts the processes, with the slab being first formed and then rolled is, and is made by two heat treatments. With two high-temperature diffusion heating processes and high penetration rolling processes, the segregations are completely diffused and the loose imperfections are pressed together. Regarding the heat treatment, the following processes are applied: normalization + water accelerated cooling + tempering heat treatment. Regulating the microstructure makes the metallographic structure more uniform and finer. The performances of the steel plate are significantly improved, in particular the impact strength at low temperatures and the resistance to hydrogen-induced cracking of the core.

• Die Erfindung betrifft eine Stahlplatte mit großer Dicke für einen Druckbehälter und mit Beständigkeit gegen wasserstoffinduzierte Rissbildung. Die Dicke beträgt >200-250mm. Die Stahlplatte verfügt über gut abgestimmte umfassende mechanische Eigenschaften und eine ausgezeichnete Beständigkeit gegen wasserstoffinduzierte Risse. Nach einer simulierten Wärmebehandlung nach dem Schweißen bei hoher Temperatur über einen längeren Zeitraum werden die Festigkeit und die Schlagzähigkeit der Stahlplatte bei niedrigen Temperaturen nicht wesentlich geschwächt. Die Stahlplatte wird durch die Lösung A gemäß der „Experimentelle Methode zur Leistungsbewertung von Pipeline-Druckbehältern um die Beständigkeit gegen wasserstoffinduzierte Rissbildung „in NACE TM0284-2016 auf Beständigkeit gegen wasserstoffinduzierte Rissbildung getestet. Das Risslängenverhältnis (CLR), das Rissbreitenverhältnis (CTR) und das Rissempfindlichkeitsverhältnis (CSR) eines einzelnen Inspektionsabschnitts sind alle 0, und es gibt keine Wasserstoffblasenbildung, d. h. keine Defekte nach der Korrosion. Nach der simulierten Wärmebehandlung nach dem Schweißen bei 610 ± 10°C × 30 Stunden werden die mechanischen Eigenschaften überprüft und die Streckgrenze ≥ 320 MPa, die Zugfestigkeit ≥ 520 MPa, der Einzelwert der Charpy-Schlagarbeit in dem Kern bei -30 °C in Querrichtung ≥ 100 J und die Reduktionsrate des Zugabschnitts in Z-Richtung ≥ 35 %, Brinellhärte der Stahlplattenoberfläche ≤ 180 HB. (Die Reduzierungsrate der Zugfläche in Z-Richtung beträgt ≥35 %, und die Brinell-Oberflächenhärte der Stahlplatte beträgt ≤180HB.)

Compared to the prior art, the invention offers the following advantages:

• The invention relates to a steel plate having a large thickness for a pressure vessel and having resistance to hydrogen-induced cracking. The thickness is >200-250mm. The steel plate has well-balanced comprehensive mechanical properties and excellent resistance to hydrogen-induced cracking. After a long-term simulated post-weld heat treatment at high temperature, the strength and impact resistance of the steel plate at low temperatures are not significantly weakened. The steel plate is tested for resistance to hydrogen induced cracking by solution A according to the “Experimental Method for Evaluating the Performance of Pipeline Pressure Vessels for Resistance to Hydrogen Induced Cracking” in NACE TM0284-2016. The crack length ratio (CLR), crack width ratio (CTR), and crack sensitivity ratio (CSR) of a single inspection section are all 0, and there is no hydrogen blistering, ie, no post-corrosion defects. After the simulated heat treatment after welding at 610 ± 10°C × 30 hours, the mechanical properties are checked and the yield strength ≥ 320 MPa, the tensile strength ≥ 520 MPa, the single value of the Charpy impact work in the core at -30 °C in the transverse direction ≥ 100 J and the reduction rate of the tensile section in the Z direction ≥ 35%, Brinell hardness of the steel plate surface ≤ 180 HB. (The Z-direction tensile area reduction rate is ≥35%, and the Brinell surface hardness of the steel plate is ≤180HB.)

character list

• 1 Fig. 14 is a metallographic structure diagram of a steel plate having a thickness of 250 mm in Example 3 of the invention (at the position of 1/4 of the thickness).
• 2 Fig. 14 is a metallographic structure diagram of a steel plate having a thickness of 250 mm in Example 3 of the invention (at the position of 1/2 the thickness).
• 3 Fig. 14 is a metallographic structure diagram of a steel plate having a thickness of 250 mm in Example 3 of the invention (at the 3/4 thickness position).

Detailed embodiment

The invention is described below in more detail in connection with examples and comparative examples.

example 1

The steel plate for pressure vessels in Example 1, having a thickness of 210mm and having resistance to hydrogen-induced cracking, the chemical composition of the steel plate in percentage by weight is: C: 0.15%, Si: 0.28%, Mn: 1.23%, P: 0.004% , S: ≤0.0006%, Cr: 0.20%, Ni: 0.32%, Mo: 0.10% , Alt: 0.032%, Nb: 0.015%, V: 0.015%, Ti: 0.015%, the balance is Fe and unavoidable impurity elements, Carbon equivalent Ceq: ≤0.45%, where Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15.

• Das Stahlplattenprodukt der Erfindung wird durch Verbundbramme hergestellt, und die Hauptprozessschritte sind nacheinander: Schmelzen und Gießen von Stranggussrohlinge, Herstellung von Verbundbramme durch Vakuumschweißen und Montage, Walzen der Verbundbramme zur Formung, Walzen zur fertigen Stahlplatte und Wärmebehandlung. Die spezifischen Vorgänge sind wie folgt:

The manufacturing process of the steel plate is as follows:

• The steel plate product of the invention is manufactured by composite slab, and the main process steps are sequentially: melting and casting of continuous cast ingots, manufacturing of composite slab by vacuum welding and assembly, rolling of composite slab to form, rolling into finished steel plate, and heat treatment. The specific operations are as follows:

(1) Melting and casting of continuous cast ingots

The continuously cast slabs produced by the same melting furnace and having the same size with a 450 mm thick section serve as the composite slab blanks. The melting process of pure steel is used in the production of continuous cast billets. Some measures, such as using a large tundish in casting and increasing the argon soft blowing time, can completely float the nonmetallic inclusions into the slag, thereby reducing the nonmetallic inclusion content of the steel and improving the purity of the molten steel. The non-metallic inclusions of type A, type B, type C and type D in the molten steel are controlled so that the index of each type of inclusions is ≦1.0 and their sum is ≦2.5. Through low superheat, argon protective casting process and dynamic soft reduction technology, the continuous casting billets are controlled so that the segregation of type C has an index below 1.0 and the porosity has an index below 0.5. After the continuous cast ingots leave the assembly line, they are covered and slowly cooled for ≥72 hours to fully diffuse the hydrogen;

In addition, the production process of continuous cast ingots is: KR pretreatment —> converter melting → LF refining → RH refining → continuous casting. After the converter melting, a slag removal treatment is performed. After the RH vacuum is broken, the soft argon blowing takes 35 minutes. In the continuous casting process, the degree of overheating of the molten steel is 22 °C.

(2) Manufacture of composite slab by vacuum welding and assembly

A surface of the continuously cast billet is milled and assembled by electron beam welding in a vacuum chamber, and the billet assembling method is that two billets are joined. The composite slab is manufactured using a conventional method that has been disclosed and the thickness of the composite slab obtained is 865 mm.

(3) Rolling the composite slab to form

The composite slab is heated in a holding furnace. While the ingot segregation is fully diffused, the partial metallurgical bonding of the composite interface is completed by high temperature diffusion. In the roughing mill, the single-stand rolling process with high penetration is adopted, and the rolling passes are appropriately distributed. Through repeated recrystallization, the bonded interface achieves a strong metallurgical bond. The thickness of the intermediate slab is 425 mm. After the intermediate slabs leave the assembly line after rolling, they are placed in a cover and slowly cooled for ≥72 hours to fully diffuse the hydrogen.

In addition, the composite slab undergoes a segmented heating process. The steel is stressed at 540°C and the steel is held for 2 hours. In the low-temperature range, the temperature is increased at a rate of 70 °C/h to 835 °C and held for 4 hours. In the medium-temperature range, the temperature is increased at a rate of 100 °C/h to 1010 °C and held for 2 hours; in the high-temperature area, the temperature is increased to 1245 °C and held for 11 hours.

In addition, the main task of forming the composite slab is to complete the rolling and joining in the roughing mill and obtain an intermediate slab of reasonable size. The initial rolling temperature is 1080°C and the final rolling temperature is 970°C. A high penetration rolling process is used. There are 4 rolling passes in longitudinal rolling, the reduction in each single pass is ≥50mm, 55mm, 55mm, 52mm, 52mm respectively.

After the steel plate leaves the assembly line, it is covered and slowly cooled for ≥72 hours.

(4) Rolling into finished steel plate

After slow cooling and finishing, the intermediate slab is reheated in a step-by-step heating furnace to make it fully austenitized. The second high-temperature diffusion heating further reduces the segregation defects in the core of the slab and at the same time provides favorable conditions for the realization of the second high-penetration rolling. In addition, the intermediate slab is gradually heated. The total heating time is 620 minutes, the second stage heating temperature is 1200-1250℃, the soaking stage temperature is 1180-1250℃, the sum of the second stage heating time and the soaking stage heating time is 300 minutes to ensure sufficient diffusion to ensure segregation.

Rolling is divided into two stages: rough rolling and finish rolling. The rolling deformation is mainly concentrated in the rough rolling stage, which adopts the high penetration rolling process. There are 2 rolling passes where the reduction in each individual pass is ≥50mm, 56mm and 52mm respectively. The main task of finish rolling is to precisely control the thickness tolerance and keep a good shape. The start rolling temperature of finish rolling is 820°C. The thickness of the serviceable steel plate is 240 mm. After the steel plate leaves the assembly line, they are stacked and slowly cooled, and slowly cooled for ≥48 hours to fully diffuse the hydrogen.

(5) Heat treatment: The steel plate is successively normalized and tempered. After normalization, water in the water tank is used to speed up cooling.

In addition, the heating temperature when normalizing is 900°C, and the holding time coefficient: 2.0 min/mm. After leaving the furnace, the steel plate is cooled with water to cool the surface of the steel plate to 450°C. In order to prevent the strength of the steel plate from greatly decreasing after the simulated post-weld heat treatment, the tempering temperature of the steel plate is the invention tion not lower than the temperature of the simulated post-weld heat treatment. When tempering: tempering temperature 630 °C, holding time coefficient: 3.5 min/mm.

The 210mm-thick steel plate for pressure vessels with resistance to hydrogen-induced cracking produced by the above production method has well-balanced mechanical properties and excellent resistance to hydrogen-induced cracking. The mechanical properties are listed in Table 1 and the resistance to hydrogen induced cracking is listed in Table 2. The steel sheet flaw detection results meet the requirements of the TI level of the NB/T47013.3 standard.

example 2

The steel plate for pressure vessels in Example 2, having a thickness of 230mm and having resistance to hydrogen-induced cracking, the chemical composition of the steel plate in percentage by weight is: C: 0.14%, Si: 0.27%, Mn: 1.26%, P: 0.003% , S: ≤0.0004%, Cr: 0.21%, Ni: 0.35%, Mo: 0.10%, Alt: 0.030%, Nb: 0.016%, V: 0.020%, Ti: 0.017%, the balance is Fe and unavoidable impurity elements, Carbon equivalent Ceq: ≤0.45%, where Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15.

• Das Stahlplattenprodukt der Erfindung wird durch Verbundbramme hergestellt, und die Hauptprozessschritte sind nacheinander: Schmelzen und Gießen von Stranggussrohlinge, Herstellung von Verbundbramme durch Vakuumschweißen und Montage, Walzen der Verbundbramme zur Formung, Walzen zur fertigen Stahlplatte und Wärmebehandlung. Die spezifischen Vorgänge sind wie folgt:

The manufacturing process of the steel plate is as follows:

• The steel plate product of the invention is manufactured by composite slab, and the main process steps are sequentially: melting and casting of continuous cast ingots, manufacturing of composite slab by vacuum welding and assembly, rolling of composite slab to form, rolling into finished steel plate, and heat treatment. The specific operations are as follows:

(1) Melting and casting of continuous cast ingots

The continuously cast slabs produced by the same melting furnace and having the same size with a 450 mm thick section serve as the composite slab blanks. The melting process of pure steel is used in the production of continuous cast billets. Some measures, such as using a large tundish in casting and increasing the argon soft blowing time, can completely float the nonmetallic inclusions into the slag, thereby reducing the nonmetallic inclusion content of the steel and improving the purity of the molten steel. The non-metallic inclusions of type A, type B, type C and type D in the molten steel are controlled so that the index of each type of inclusions is ≦1.0 and their sum is ≦2.5. Through low superheat, argon protective casting process and dynamic soft reduction technology, the continuous casting billets are controlled so that the segregation of type C has an index below 1.0 and the porosity has an index below 0.5. After the continuous cast ingots leave the assembly line, they are covered and slowly cooled for ≥72 hours to fully diffuse the hydrogen;

In addition, the production process of continuous cast ingots is: KR pretreatment → converter smelting → LF refining → RH refining → continuous casting. After the converter melting, a slag removal treatment is performed. After the RH vacuum is broken, the argon soft blow lasts 32 minutes. In the continuous casting process, the degree of overheating of the molten steel is 20 °C.

(2) Manufacture of composite slab by vacuum welding and assembly

A surface of the continuously cast billet is milled and assembled by electron beam welding in a vacuum chamber, and the billet assembling method is that two billets are joined. The composite slab is manufactured using a conventional method that has been disclosed and the thickness of the composite slab obtained is 868 mm.

(3) Rolling the composite slab to form

The composite slab is heated in a holding furnace. While the ingot segregation is fully diffused, the partial metallurgical bonding of the composite interface is completed by high temperature diffusion. In the roughing mill, the single-stand rolling process with high penetration is adopted, and the rolling passes are appropriately distributed. Through repeated recrystallization, the bonded interface achieves a strong metallurgical bond. The thickness of the intermediate slab is 440 mm. After the intermediate slabs leave the assembly line after rolling, they are placed in a cover and slowly cooled for ≥72 hours to fully diffuse the hydrogen.

In addition, the composite slab undergoes a segmented heating process. The steel is stressed at 530°C and the steel is held for 2 hours. In the low-temperature range, the temperature is increased at a rate of 65 °C/h to 835 °C and held for 4.5 hours. In the middle temperature range, the temperature is increased at a rate of 105 °C/h to 1020 °C and held for 2 hours; in the high-temperature area, the temperature is increased to 1242 °C and held for 10 hours.

In addition, the main task of forming the composite slab is to complete the rolling and joining in the roughing mill and obtain an intermediate slab of reasonable size. The initial rolling temperature is 1070°C and the final rolling temperature is 975°C. A high penetration rolling process is used. There are 4 rolling passes in longitudinal rolling, the reduction in each single pass is ≥50mm, 55mm, 55mm, 55mm, 52mm respectively.

After the steel plate leaves the assembly line, it is covered and slowly cooled for ≥72 hours.

(4) Rolling into finished steel plate

After slow cooling and finishing, the intermediate slab is reheated in a step-by-step heating furnace to make it fully austenitized. The second high-temperature diffusion heating further reduces the segregation defects in the core of the slab and at the same time provides favorable conditions for the realization of the second high-penetration rolling. In addition, the intermediate slab is gradually heated. The total heating time is 620 minutes, the second stage heating temperature is 1200-1250℃, the soaking stage temperature is 1180-1250℃, the sum of the second stage heating time and the soaking stage heating time is 310 minutes to ensure sufficient diffusion to ensure segregation.

Rolling is divided into two stages: rough rolling and finish rolling. The rolling deformation is mainly concentrated in the rough rolling stage, which adopts the high penetration rolling process. There are 2 rolling passes, the reduction in each individual pass is ≥50mm, 55mm and 55mm respectively. The main task of finish rolling is to precisely control the thickness tolerance and keep a good shape. The start rolling temperature of finish rolling is 810°C. The thickness of the serviceable steel plate is 270 mm. After the steel plate leaves the assembly line, they are stacked and slowly cooled, and slowly cooled for ≥48 hours to fully diffuse the hydrogen.

(5) Heat treatment: The steel plate is successively normalized and tempered. After normalization, water in the water tank is used to speed up cooling.

In addition, the normalizing heating temperature is 900°C, and the holding time coefficient: 2.2 min/mm. After leaving the furnace, the steel plate is cooled with water to cool the surface of the steel plate to 420°C. In order to prevent the strength of the steel plate after the post-weld simulated heat treatment from greatly decreasing, the tempering temperature of the steel plate of the invention is not lower than the post-weld simulated heat treatment temperature. When tempering: tempering temperature 620 °C, holding time coefficient: 4.0 min/mm.

The 230mm-thick steel plate for pressure vessels with resistance to hydrogen-induced cracking produced by the above production method has well-balanced mechanical properties and excellent resistance to hydrogen-induced cracking. The mechanical properties are listed in Table 1 and the resistance to hydrogen induced cracking is listed in Table 2. The steel sheet flaw detection results meet the requirements of the TI level of the NB/T47013.3 standard.

Example 3

The steel plate for pressure vessels in Example 3, having a thickness of 250 mm and having resistance to hydrogen-induced cracking, the chemical composition of the steel plate being in Weight percent is: C: 0.13%, Si: 0.32%, Mn: 1.32%, P: 0.004%, S: ≤0.0005%, Cr: 0.22%, Ni: 0.36%, Mo: 0.11%, Alt: 0.028%, Nb : 0.018%, V: 0.025%, Ti: 0.016%, the balance is Fe and unavoidable impurity elements, carbon equivalent Ceq: ≤0.45%, where Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni +Cu) /15.

• Das Stahlplattenprodukt der Erfindung wird durch Verbundbramme hergestellt, und die Hauptprozessschritte sind nacheinander: Schmelzen und Gießen von Stranggussrohlinge, Herstellung von Verbundbramme durch Vakuumschweißen und Montage, Walzen der Verbundbramme zur Formung, Walzen zur fertigen Stahlplatte und Wärmebehandlung. Die spezifischen Vorgänge sind wie folgt:

The manufacturing process of the steel plate is as follows:

• The steel plate product of the invention is manufactured by composite slab, and the main process steps are sequentially: melting and casting of continuous cast ingots, manufacturing of composite slab by vacuum welding and assembly, rolling of composite slab to form, rolling into finished steel plate, and heat treatment. The specific operations are as follows:

(1) Melting and casting of continuous cast ingots

The continuously cast slabs produced by the same melting furnace and having the same size with a 450 mm thick section serve as the composite slab blanks. The melting process of pure steel is used in the production of continuous cast billets. Some measures, such as using a large tundish in casting and increasing the argon soft blowing time, can completely float the nonmetallic inclusions into the slag, thereby reducing the nonmetallic inclusion content of the steel and improving the purity of the molten steel. The non-metallic inclusions of type A, type B, type C and type D in the molten steel are controlled so that the index of each type of inclusions is ≦1.0 and their sum is ≦2.5. Through low superheat, argon protective casting process and dynamic soft reduction technology, the continuous casting billets are controlled so that the segregation of type C has an index below 1.0 and the porosity has an index below 0.5. After the continuous cast ingots leave the assembly line, they are covered and slowly cooled for ≥72 hours to fully diffuse the hydrogen;

In addition, the production process of continuous cast ingots is: KR pretreatment → converter smelting → LF refining → RH refining → continuous casting. After the converter melting, a slag removal treatment is performed. After the RH vacuum is broken, the argon soft blow lasts 38 minutes. In the continuous casting process, the degree of overheating of the molten steel is 23 °C.

(2) Manufacture of composite slab by vacuum welding and assembly

A surface of the continuously cast billet is milled and assembled by electron beam welding in a vacuum chamber, and the billet assembling method is that two billets are joined. The composite slab is manufactured using a conventional method that has been disclosed and the thickness of the composite slab obtained is 870 mm.

(3) Rolling the composite slab to form

The composite slab is heated in a holding furnace. While the ingot segregation is fully diffused, the partial metallurgical bonding of the composite interface is completed by high temperature diffusion. In the roughing mill, the single-stand rolling process with high penetration is adopted, and the rolling passes are appropriately distributed. Through repeated recrystallization, the bonded interface achieves a strong metallurgical bond. The thickness of the intermediate slab is 450 mm. After the intermediate slabs leave the assembly line after rolling, they are placed in a cover and slowly cooled for ≥72 hours to fully diffuse the hydrogen.

In addition, the composite slab undergoes a segmented heating process. The steel is stressed at 545°C and the steel is held for 2 hours. In the low-temperature range, the temperature is increased at a rate of 60 °C/h to 820 °C and held for 4 hours. In the middle temperature range, the temperature is increased at a rate of 110 °C/h to 1020 °C and held for 2 hours; in the high-temperature area, the temperature is increased to 1250 °C and maintained for 12 hours.

In addition, the main task of forming the composite slab is to complete the rolling and joining in the roughing mill and obtain an intermediate slab of reasonable size. The initial rolling temperature is 1100°C and the final rolling temperature is 980°C. A rolling process with high penetration is applied. There are 4 rolling passes in longitudinal rolling, the reduction in each single pass is ≥50mm, 55mm, 55mm, 55mm, 55mm respectively.

After the steel plate leaves the assembly line, it is covered and slowly cooled for ≥72 hours.

(4) Rolling into finished steel plate

After slow cooling and finishing, the intermediate slab is reheated in a step-by-step heating furnace to make it fully austenitized. The second high-temperature diffusion heating further reduces the segregation defects in the core of the slab and at the same time provides favorable conditions for the realization of the second high-penetration rolling. In addition, the intermediate slab is gradually heated. The total heating time is 620 minutes, the second stage heating temperature is 1200-1250℃, the soaking stage temperature is 1180-1250℃, the sum of the second stage heating time and the soaking stage heating time is 320 minutes to ensure sufficient diffusion to ensure segregation.

Rolling is divided into two stages: rough rolling and finish rolling. The rolling deformation is mainly concentrated in the rough rolling stage, which adopts the high penetration rolling process. There are 2 rolling passes where the reduction in each individual pass is ≥50mm, 56mm and 56mm respectively. The main task of finish rolling is to precisely control the thickness tolerance and keep a good shape. The start rolling temperature of finish rolling is 800°C. The thickness of the serviceable steel plate is 280 mm. After the steel plate leaves the assembly line, they are stacked and slowly cooled, and slowly cooled for ≥48 hours to fully diffuse the hydrogen.

(5) Heat treatment: The steel plate is successively normalized and tempered. After normalization, water in the water tank is used to speed up cooling.

In addition, the heating temperature when normalizing is 900 °C, and the holding time coefficient: 2.5 min/mm. After leaving the furnace, the steel plate is cooled with water to cool the surface of the steel plate to 400°C. In order to prevent the strength of the steel plate after the post-weld simulated heat treatment from greatly decreasing, the tempering temperature of the steel plate of the invention is not lower than the post-weld simulated heat treatment temperature. When tempering: tempering temperature 610 °C, holding time coefficient: 4.5 min/mm.

The 250mm-thick steel plate for pressure vessels with resistance to hydrogen-induced cracking produced by the above production method has well-balanced mechanical properties and excellent resistance to hydrogen-induced cracking. The mechanical properties are listed in Table 1 and the resistance to hydrogen induced cracking is listed in Table 2. The steel sheet flaw detection results meet the requirements of the TI level of the NB/T47013.3 standard. Steel plate metallographic structure is Ferrite + Tempered Bainite. The microstructures are in the 1 until 3 shown. Table 1: Mechanical properties of the steel plate produced in each example Example thick mm test report Trial condition and sample took eort yield strength MPa Tensile strength MPa Elongation and 9% Charpy V impact work at -30 °C KV8/J Z-direction drawing section reduction rate % Brinell surface hardness HB 1 210 transverse direction Normalizing + water-accelerated cooling + tempering 1/4 the thickness 350 552 30 178,175,182 65,65,68 178, 177, 178 1/2 the thickness 342 545 32 208,194,167 3/4 the thickness 352 548 31 166,162,188 Normalizing + water-accelerated cooling + tempering + simulated post-weld heat treatment 1/4 the thickness 330 531 31 164,152,174 62,65,65 174, 172, 172 1/2 the thickness 322 525 30 196,182,175 3/4 the thickness 328 522 29 154,162,185 2 230 transverse direction Normalizing + water-accelerated cooling + tempering 1/4 the thickness 346 548 30 168,145,132 62,62,66 176, 174, 175 1/2 the thickness 340 542 30 197,164,168 3/4 the thickness 341 544 31 146,152,108 Normalizing + water-accelerated cooling + tempering + simulated post-weld heat treatment 1/4 the thickness 330 531 28 127,155,132 61,61,60 170, 171, 172 1/2 the thickness 322 525 30 148,164,168 3/4 the thickness 328 522 29 115,122,127 3 250 across dir Normalize + 1/4 of the 338 552 30 138,105,122 60,64,58 174, 177, ng water-accelerated cooling + temperature control thickness 175 1/2 the thickness 342 545 32 153,154,145 3/4 the thickness 345 548 31 134,114,109 Normalizing + water-accelerated cooling + tempering + simulated post-weld heat treatment 1/4 the thickness 325 527 30 128,115,102 57,58,62 172, 167, 172 1/2 the thickness 330 529 32 116,115,135 3/4 the thickness 327 526 31 107,121,113
Note: simulated heat treatment after welding: 610±10°C×30h _∘ Table 2: Resistance to hydrogen induced cracking (HIC) of the steel plate produced in each example Example sample no Part 1 Section 2 Section 3 Hydrogen blistering (HB) CSR % CLR% CTR% CSR % CLR% CLR% CTR% CSR % CLR% 1 sample 1 0 0 0 0 0 0 0 0 0 no sample 2 0 0 0 0 0 0 0 0 0 no sample 3 0 0 0 0 0 0 0 0 0 no sample 4 0 0 0 0 0 0 0 0 0 no sample 5 0 0 0 0 0 0 0 0 0 no rehearsal 6 0 0 0 0 0 0 0 0 0 no rehearsal 7 0 0 0 0 0 0 0 0 0 no rehearsal 8 0 0 0 0 0 0 0 0 0 no 2 sample 1 0 0 0 0 0 0 0 0 0 no sample 2 0 0 0 0 0 0 0 0 0 no sample 3 0 0 0 0 0 0 0 0 0 no sample 4 0 0 0 0 0 0 0 0 0 no sample 5 0 0 0 0 0 0 0 0 0 no rehearsal 6 0 0 0 0 0 0 0 0 0 no rehearsal 7 0 0 0 0 0 0 0 0 0 no rehearsal 8 0 0 0 0 0 0 0 0 0 no rehearsal 9 0 0 0 0 0 0 0 0 0 no 3 sample 1 0 0 0 0 0 0 0 0 0 no sample 2 0 0 0 0 0 0 0 0 0 no sample 3 0 0 0 0 0 0 0 0 0 no sample 4 0 0 0 0 0 0 0 0 0 no sample 5 0 0 0 0 0 0 0 0 0 no rehearsal 6 0 0 0 0 0 0 0 0 0 no rehearsal 7 0 0 0 0 0 0 0 0 0 no rehearsal 8 0 0 0 0 0 0 0 0 0 no rehearsal 9 0 0 0 0 0 0 0 0 0 no

In addition to the above embodiments, the invention also encompasses other implementations, and the technical solution resulting from equivalent transformation or equivalent replacement falls within the scope of the claims of the invention.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• CN10108330398A [0004]
• CN 111349859A [0004]
• CN 109355579A [0004]
• CN 108754321B [0004]

Claims (9)

A steel plate for pressure vessels, having a thickness of more than 200 to 250 mm and having resistance to hydrogen induced cracking, characterized in that the chemical composition of the steel plate in percentage by weight is: C: 0.10-0.20%, Si: 0, 15-0.40%, Mn: 0.95-1.35%, P: ≤0.005%, S: ≤0.0008%, Cr: 0.10-0.30%, Ni: 0.25-0 .40%, Mo: 0.08-0.12%, Old: 0.02-0.05%, Nb: 0.01-0.02%, V: 0.01-0.03%, Ti: 0.01 - 0.02%, B: ≤ 0.0005%, the balance is Fe and unavoidable impurity elements. The steel plate for pressure vessels, with a thickness of more than 200 to 250 mm and with resistance to hydrogen induced cracking claim 1 , characterized in that the chemical composition of the steel plate corresponds to the carbon equivalent Ceq≤0.45%, where Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15. Method of manufacturing the steel plate for pressure vessels with a thickness of more than 200 to 250 mm and with resistance to hydrogen induced cracking claim 1 , characterized in that the manufacturing process comprises: melting and casting of continuously cast ingots, manufacture of composite slab by vacuum welding and assembly, rolling of composite slab to form, rolling into finished steel plate and heat treatment. procedure after claim 3 , for the production of the steel plate for pressure vessels with a thickness of more than 200 to 250 mm and with resistance to hydrogen induced cracking, characterized in that the process comprises as follows: (1) Continuous cast slabs produced by the same melting furnace and the same size Having sections serve as blanks of the composite slab; in the production of continuous casting billets, the melting process for pure steel is used; through the use of a large tundish in the casting and the extension of the time of gentle argon blowing, the nonmetallic inclusions completely float up into the slag, thereby reducing the content of nonmetallic inclusions in the steel and improving the purity of the molten steel, the nonmetallic inclusions type A, type B, type C and type D in the molten steel are controlled so that the index of each type of inclusions is ≦1.0 and their sum is ≦2.5; through low superheat, argon protective casting process and dynamic soft reduction technology, the continuous casting billets are controlled so that the segregation of type C has an index below 1.0 and the porosity has an index below 0.5; after the continuous cast ingots leave the assembly line, they are covered and slowly cooled for ≥72 hours to fully diffuse the hydrogen; (2) a surface of the continuously cast billet is milled and assembled by electron beam welding in a vacuum chamber, and the billet assembling method is that two billets are joined; (3) the composite slab is heated in a holding furnace; while the ingot segregation is fully diffused, the partial metallurgical bonding of the composite interface is completed by high temperature diffusion; in the roughing mill, the single-stand rolling process with high penetration is adopted, and the rolling passes are distributed appropriately; through repeated recrystallization, the bonded interface achieves a strong metallurgical bond; the thickness of the intermediate slab is controlled to 400-450 mm; after the intermediate slab exits the assembly line after rolling, it is placed in a cover and slowly cooled for ≥72 hours to fully diffuse the hydrogen; (4) after slow cooling and finishing, the intermediate slab is reheated in a step-by-step heating furnace to make it fully austenitized; the second high-temperature diffusion heating further reduces the segregation defects in the core of the slab and at the same time provides favorable conditions for the realization of the second high-penetration rolling; (5) the steel plate is successively normalized and tempered; after normalization, water in the water tank is used to speed up cooling. procedure after claim 4 , for the production of the steel plate for pressure vessels with a thickness of more than 200-250 mm and with resistance to hydrogen-induced cracking, characterized in that the production process of the continuously cast ingots is: KR pretreatment → converter smelting → LF refining → RH refining → continuous casting, wherein after the converter melting, a slag removal treatment is performed; after the RH vacuum is broken argon soft blowing takes more than 30 minutes; in the continuous casting process, the degree of overheating of the steel melt is 10 to 30 °C, preferably 10 to 25 °C. procedure after claim 4 , for the production of the steel plate for pressure vessels with a thickness of more than 200 to 250 mm and with resistance to hydrogen-induced cracking, characterized in that the composite slab is subjected to a segmented heating process: the steel is stressed at below 550°C and the steel is 1 keep for up to 2 hours; in the low-temperature range, the temperature is raised to 820 ± 20 °C at a rate not exceeding 75 °C/h and maintained for 3 to 5 hours; in the medium-temperature range, the temperature is raised to 1000 ± 20 °C at a rate not exceeding 110 °C/h and maintained for 2 hours; in the high temperature range, the temperature is increased to 1220-1250 °C and maintained for 8 to 12 hours. procedure after claim 4 , for the production of the steel plate for pressure vessels with a thickness of more than 200 to 250 mm and having resistance to hydrogen-induced cracking, characterized in that the process for forming the composite slab is to complete the rolling and bonding in the roughing mill and to obtain an intermediate slab, wherein the Initial rolling temperature is 1060-1100℃ and final rolling temperature is 950-980℃, adopting high penetration rolling method, there are at least 4 rolling passes in longitudinal rolling, each with a reduction of ≥ 50mm; after the steel plate leaves the assembly line, it is covered and slowly cooled for ≥ 72 hours. procedure after claim 4 , for the production of the steel plate for pressure vessels with a thickness of more than 200-250 mm and with resistance to hydrogen-induced cracking, characterized in that the intermediate slab is heated in stages, the total heating time is 620 minutes, the temperature of the second stage heating is 1200-1250 ° C, the temperature of the soaking stage is 1180-1250 °C, the sum of the heating time of the second heating stage and the heating time of the soaking stage is ≥270 minutes to ensure sufficient diffusion of segregations; rolling is divided into two stages: rough rolling and finish rolling, the rolling deformation is mainly concentrated in the rough rolling stage, which adopts high penetration rolling method, there are at least 2 rolling passes, each with a reduction of ≥ 50mm; the main task of finish rolling is to precisely control a thickness tolerance and keep a good shape; the initial rolling temperature of finish rolling is 820 ± 20 °C; the thickness of a waiting steel plate is the thickness of the finished steel plate plus 30mm; after the steel plate leaves the assembly line, they are stacked and slowly cooled, and slowly cooled for ≥48 hours to fully diffuse the hydrogen. procedure after claim 4 , for the production of the steel plate for pressure vessels with a thickness of more than 200-250 mm and with resistance to hydrogen-induced cracking, characterized in that the heating temperature in normalizing is 880-910 °C and the holding time coefficient is 2.0-2.5 min/ mm is; after removing from the furnace, the steel plate is cooled with water to cool the surface of the steel plate to 400-500°C; Tempering temperature 610-630 °C, holding time coefficient: 3.5-4.5 min/mm.