CN109161671B - High-strength EH36 steel plate for high heat input welding and manufacturing method thereof - Google Patents
High-strength EH36 steel plate for high heat input welding and manufacturing method thereof Download PDFInfo
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D2211/002—Bainite
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention relates to a high-strength EH36 steel plate for high heat input welding, which is prepared by smelting the following components in percentage by weight: c: 0.06% -0.18%, Si: 0.15-0.50%, Mn: 1.10-1.60%, P is less than or equal to 0.012%, S is less than or equal to 0.003%, Ni: 0.10% -0.40%, Nb: 0.010% -0.030%, Al: less than or equal to 0.010 percent, Ti: 0.010% -0.030%, Ca: 0.001 to 0.010 percent, and the balance of Fe and inevitable impurities. The maximum thickness of the steel plate is 100mm, the yield strength is more than or equal to 355MPa, the tensile strength is more than or equal to 510MPa, the low-temperature impact absorption energy KV2 at minus 40 ℃ is more than or equal to 150KJ, and the production method of the steel plate comprises the following steps: smelting → LF/RH refining → continuous casting → heating → rolling → rapid cooling → finished steel plate. The steel plate produced by the method has the characteristics of higher purity, high strength, good low-temperature impact energy, capability of keeping good toughness when the maximum input line energy is 300KJ/CM and the like, can be widely applied to the fields of shipbuilding, bridges, building structures and the like, and has wide application prospect.
Description
Technical Field
The invention relates to a high-strength steel plate EH36 for high heat input welding used for manufacturing large ships, large bridges and large mechanical equipment, and also relates to a production method of the steel plate. Belongs to the technical field of metallurgy.
Background
In recent years, with the upsizing of steel structures, steel materials are required to have high strength and increased thickness, and because the energy of a welding input line of the traditional large-thickness high-strength steel is less than 100KJ/CM, the welding efficiency is low, the improvement of welding construction efficiency is urgently required, and the further development of high linear energy welding coping technology is required along with the improvement of the welding efficiency. Under the condition, the invention provides a high-strength steel plate for high heat input welding and also relates to a production method of the steel plate. The high-strength steel plate for high heat input welding with the maximum welding energy of 300KJ/CM, the maximum thickness specification of 100mm and the yield strength of not less than 355MPa is developed by an oxide metallurgy process for improving the structure and the toughness of HAZ by using fine inclusions in steel through the technology of refining bainite structure and reducing MA (island martensite hardened structure) at the HAZ (heat affected zone) for high heat input welding with low carbon and adding a proper amount of weak carbide forming elements. The successful development of the steel plate with the thickness, the strength level and the allowed welding input line energy value has important significance for the localization and further popularization and application of the steel plate with the level.
The quality difficulty of the high heat input welding steel is mainly shown in the following steps:
1. the produced steel plate is thicker and thicker, generally more than 50mm, and the maximum thickness reaches 100 mm;
2. the toughness requirement is high, the-40 ℃ transverse impact absorption energy KV2 is required to be more than 150J, meanwhile, the high strength is required, and the performance guarantee difficulty of the steel plate is extremely high;
3. the requirement on the large heat input resistance welding performance is high, and the strength of the steel plate and the low-temperature toughness of a welding fusion line and a welding heat affected zone can still meet the standard requirement when the maximum welding heat input energy reaches 300KJ/CM (kilomega watt/centimeter) (-40 ℃ transverse impact absorption energy KV2 reaches more than 150J).
The patent (CN104404369A) applies for a large heat input welding thick steel plate and a manufacturing method thereof, which improves the large heat input welding resistance by adding Mg and Ca alloy and controlling the size and distribution of micron-sized and submicron-sized inclusions in the steel, can resist the welding of 200KJ/cm-400KJ/cm ultra-large heat input, has excellent obdurability, has an average Charpy impact power at-40 ℃ of more than 50J, but Mg is an element which is easy to be oxidized, is difficult to control the alloy addition and the size and the content of the micron-sized inclusions in industrial production, brings great difficulty to the production, and has poor operability.
The patent (CN102839320A) applies for a steel plate for high heat input welding produced by TMCP technology, the tensile strength is more than or equal to 550MPa, the steel plate can resist the high heat input welding of 100-200 KJ/cm, the impact toughness of a base metal and a welding heat affected zone at the temperature of-20 ℃ is more than 150J, but the content of N is controlled to be 0.006-0.020%, trace B element is added, the heat input welding energy is small, and the requirement of high heat input welding is difficult to meet.
The patent (CN101724779B) discloses a high-toughness steel and a steel plate suitable for large heat input welding, which are produced by strengthening thermomechanical rolling and post-rolling accelerated cooling process, are designed by adopting C-Mn + Nb and Ti microalloying components, have the characteristics of low carbon equivalent, excellent strength and toughness and the like, are simple in process and low in cost, but do not particularly relate to large heat input welding.
Disclosure of Invention
The present invention is directed to provide a high strength EH36 steel sheet for high heat input welding and a method for manufacturing the same, which can improve the strength and low temperature impact toughness of the steel sheet when the steel sheet is subjected to high heat input.
The technical scheme adopted by the invention for solving the problems is as follows: a high-strength EH36 steel plate for high heat input welding is prepared by smelting the following components in percentage by mass: c: 0.06% -0.18%, Si: 0.15-0.50%, Mn: 1.10-1.60%, P is less than or equal to 0.012%, S is less than or equal to 0.003%, Ni: 0.10% -0.40%, Nb: 0.010% -0.030%, Al: less than or equal to 0.010 percent, Ti: 0.010% -0.030%, Ca: 0.002% -0.010%, and the balance of Fe and inevitable impurities.
The maximum thickness of the steel plate is 100 mm.
The steel plate is designed by adopting chemical components, and is subjected to solid solution strengthening by proper carbon and manganese; a small amount of Nb refined grains are added, and the carbonitride of the Nb refined grains plays a role in dispersion strengthening; ti and Ca combine with oxygen in the steel to form high temperature resistant oxides; ni improves the low temperature toughness of the steel sheet.
The steel plate comprises the following components in percentage by weight:
c: 0.06% -0.18%, carbon has obvious influence on the yield strength, tensile strength and welding performance of steel, and proper carbon content can improve the hardenability of the steel plate, and is the most direct and economic element for improving the strength of the steel plate, thereby effectively reducing the use amount of the noble alloy element Ni. However, too high a carbon content will affect the weldability and toughness of the steel.
Si: 0.15 to 0.50 percent of the total aluminum content, which is used as a reducing agent and a deoxidizer in the steelmaking process, and simultaneously, Si can play a role in solid solution strengthening, but when the content is too high, the toughness of the steel is reduced, and the welding performance of the steel is reduced.
Mn: 1.10 to 1.60 percent of manganese, has low cost, can increase the toughness, the strength and the hardness of steel, improve the hardenability of the steel and improve the hot workability of the steel; the manganese content is too high, and center segregation is likely to occur in a large-thickness steel sheet.
P is less than or equal to 0.012 percent, and S is less than or equal to 0.005 percent: in general, phosphorus and sulfur are harmful elements in steel, so that the brittleness of the steel is increased; phosphorus deteriorates the welding property, reduces the plasticity, and deteriorates the cold bending property; sulfur reduces the ductility and toughness of the steel, causing cracks during forging and rolling; the contents of phosphorus and sulphur in the steel should therefore be minimized.
Al: al is less than or equal to 0.010 percent, and because the melting point of the oxide of Al is less than or equal to 1300 ℃, the oxide of Al can be melted when large linear energy is input and can not play a role in pinning a grain boundary, the content of Al is reduced as much as possible.
Nb: 0.010% -0.030%, niobium is added to promote grain refinement of a steel rolling microstructure, the strength and toughness can be improved simultaneously, niobium can effectively refine the microstructure by inhibiting austenite recrystallization in the controlled rolling process, and a matrix is strengthened by precipitation; niobium can reduce the overheating sensitivity and the temper brittleness of steel, segregation and precipitation of niobium atoms can prevent austenite grains from coarsening during heating in the welding process, a fine heat affected zone structure is obtained after welding, and the welding performance is improved.
Ti: 0.010-0.020%, Ca: 0.002% -0.010%, titanium and calcium are good deoxidizers, oxides of titanium and calcium can still keep particle shapes and are not dissolved at the high temperature of more than 1350 ℃, the oxides of titanium and calcium can play a role in pinning grain boundaries, so that toughness deterioration caused by coarsening of crystal grains in a welding heat affected zone is avoided, meanwhile, Ti and C, N elements can form Ti carbides, nitrides or carbonitrides, and the compounds have good grain refining effects.
Ni: 0.10 to 0.40 percent of nickel is dissolved in austenite, austenite recrystallization is inhibited, austenite grains are refined, and the low-temperature toughness of the steel plate is improved.
The invention also aims to provide a production method of the high-strength EH36 steel plate for high heat input welding, so as to improve the strength and the low-temperature impact toughness of the steel plate under the condition of high heat input.
The method for producing the high-strength steel plate for high heat input welding adopts the following technical scheme steps:
(1) smelting: the composite material comprises the following components in percentage by mass: 0.06% -0.18%, Si: 0.15-0.50%, Mn: 1.10-1.60%, P is less than or equal to 0.012%, S is less than or equal to 0.003%, Ni: 0.10% -0.40%, Nb: 0.010% -0.030%, Al: less than or equal to 0.010 percent, Ti: 0.010% -0.030%, Ca: 0.002% -0.010% of molten steel is smelted by an electric furnace or a converter, and is sent into an LF refining furnace for refining, and the molten steel is transferred into an RH furnace for vacuum degassing treatment when the temperature of the molten steel reaches or exceeds 1560 +/-10 ℃; after vacuum degassing treatment, adding Fe-Ca wire 400-500 m or pure Ca wire 300-400 m, soft blowing for 3 min to make the molten steel uniform, and then ladle-casting.
(2) Continuous casting: the method is characterized by adopting slab caster with the thickness of 150mm, 200mm, 370mm and 450mm for production, and the casting temperature is 1535-1545 ℃.
(3) Heating: the heating temperature of the continuous casting billet is 1220-1240 ℃ at the maximum, the soaking temperature is 1200-1220 ℃, and the heat preservation is carried out for 10 hours;
(4) rolling: rolling by adopting a two-stage rolling process of a recrystallization zone and a non-recrystallization zone, wherein the thickness of intermediate steel airing is 2-3 times of the thickness of a finished product plate, the rolling temperature of the first stage is 930-1100 ℃, the single-pass reduction of the first stage is 10-20%, and the accumulated reduction rate is 40-60%; the rolling temperature of the second stage is 800-880 ℃, the accumulated reduction rate is 40-60%, and a crude steel plate product is obtained;
(5) water cooling after rolling of the steel plate: after the steel plate is rolled, the steel plate is rapidly cooled by water, the steel plate is set to be in a DQ mode, the cooling speed is 10-20 ℃/s, the water quantity is automatically controlled, the water inlet temperature of the steel plate is 750-800 ℃, and the water outlet re-reddening temperature of the steel plate is 550-650 ℃.
In the refining step (1), Al is not used for deoxidation, the Al content in the steel is reduced as much as possible, in order to achieve the purpose of forming a desired oxide in the molten steel, in the early stage of the refining, weak deoxidation elements such as Si, Mn and the like are used for deoxidation, the free oxygen content in the molten steel is reduced to about 10 PPM-100 PPM, meanwhile, argon is blown greatly to enable the S in the molten steel to reach a specified value, most of Al remained in the molten steel is consumed, the Al is enabled to be less than or equal to 0.0075%, then Ti is added, a certain amount of free oxygen is contained to be combined with the Ti, a fine Ti oxide is formed in the molten steel, and coarsening of crystal grains during large-line energy welding is prevented by pinning grain boundaries by the high-. Vacuum degree of vacuum degassing treatment is not more than 66.6Pa, vacuum holding time is 10-30 minutes, Fe-Ca line 400-700 m or pure Ca line 300-600 m is added after vacuum degassing treatment, Ca is strong oxidizing element, Ca is combined with residual oxygen in steel to generate fine Ca oxide with high melting point, molten steel is uniformly blown for 3-20 minutes, and then ladle pouring is carried out. The combined action of Ti and Ca oxide can improve the high heat input welding performance of steel.
And (3) casting the cast slab into a slab with the thickness of 200mm, 250mm, 300mm and 330mm at the casting temperature of 1535-1545 ℃ in the step (2).
The thickness of the intermediate steel airing in the step (4) is 1.5 to 3 times of the thickness of a finished product plate, the initial rolling temperature of the first-stage rolling is 1050 to 1100 ℃, and the final rolling temperature is 920 to 970 ℃; the rolling temperature of the second stage is 840-880 ℃, and the finishing temperature is 800-820 ℃.
And (3) after the steel plate is rolled, setting the water cooling of the steel plate in the step (5) to be a DQ mode (direct quenching mode), wherein the cooling speed is 10-20 ℃/s, the water inlet temperature of the steel plate is 750-800 ℃, and the water outlet and red returning temperature of the steel plate is 550-650 ℃.
The steel plate has the advantages that the chemical composition design of the steel plate adopts titanium and calcium to deoxidize to form fine and high-temperature-resistant oxides to ensure the high heat input welding performance of the steel plate, simultaneously, the carbon and manganese with low price are used for solid solution strengthening, the proportion of other alloy elements in the steel plate is optimized by adjusting, and meanwhile, the controlled rolling and controlled cooling processes are adopted, so that the mechanical property of the steel plate can be ensured to be good under the condition of low precious alloy usage, the steel plate has good structure, comprehensive performance and welding performance, and the market competitiveness is enhanced; the production method of the steel plate adopts controlled rolling and controlled cooling processes, solves the problems of coarse and uneven crystal grains of the steel plate and has excellent comprehensive performance; the low-temperature toughness has quite large margin, can be widely used for shipbuilding, bridges and high-rise building engineering, and has wide application prospect; the production method of the steel plate adopts controlled rolling and controlled cooling processes to obtain ferrite, pearlite, bainite and other composite structures, and the steel plate has uniform and fine structures.
Compared with the prior art, the invention has the following beneficial effects:
the steel quality of the invention is purer, P is less than or equal to 0.012 percent, and S is less than or equal to 0.005 percent; secondly, the low-temperature impact energy is high, and the impact absorption energy KV2 is more than 150J at the temperature of minus 40 ℃; the maximum thickness of the steel plate can reach 100 mm; fourthly, the maximum welding line energy is 300 KJ/CM; fifthly, the steel plate structure is a composite structure of ferrite, pearlite, bainite and the like.
According to the invention, the problem of matching of low carbon equivalent of the steel plate and high strength and toughness of the steel plate is solved by proper proportion of carbon and alloy elements, and reasonable rolling control and cooling control process systems are combined, so that the microstructure of the steel plate reaches reasonable collocation of pearlite and polygonal ferrite with proper morphology, and the performance of the steel plate base metal and the large heat input welding can meet the use requirement. Through proper continuous casting billet specification selection, strict and reasonable steelmaking process, continuous casting process, steel plate controlled rolling and controlled cooling process, excellent macrostructure is ensured to be achieved under the conditions of large thickness and large single weight, and thus the core quality, high strength and toughness and the uniformity of the whole steel plate are ensured. The EH36 steel plate with large thickness, high strength and high toughness completely meets the use requirements of steel plates of large ships, large bridges and the like.
The steel plate does not use Al for deoxidation, and the Al content in the steel is reduced as much as possible, in order to achieve the purpose of forming a desired oxide in the molten steel, in the early stage of refining, weak deoxidation elements such as Si, Mn and the like are used for deoxidation, so that the free oxygen content in the molten steel is reduced to about 10 PPM-100 PPM, meanwhile, the argon is blown greatly to enable the S in the molten steel to reach a specified value, most of the Al remained in the molten steel is consumed, the Al is less than or equal to 0.0075%, then Ti is added, a certain amount of free oxygen is combined with the Ti, fine Ti oxide is formed in the molten steel, and the coarsening of crystal grains during large-line energy welding is prevented by pinning crystal boundaries of the high-melting point fine dispersed Ti oxide, thereby achieving the purpose of improving.
The steel plate has excellent comprehensive performance and better high heat input welding resistance, enhances the market competitiveness, fills the domestic blank, and has quality and performance indexes which meet and exceed the technical requirements of manufacturing high-strength and high-toughness steel plates for large ships and large bridges. Meanwhile, the method has the advantages of short production flow, simple process, low cost and strong operability of process parameters.
The test result shows that: the steel plate produced by the method has the characteristics of higher purity, good impact energy at-40 ℃, good high heat input welding performance and the like.
Drawings
FIG. 1 is a schematic diagram of a welding groove of high heat input steel in the embodiment of the invention, which illustrates the requirements of high heat input welding operation.
FIG. 2 is a 500-fold magnification of a metallographic structure of a weld center at a weld line energy of 250KJ/cm in an embodiment of the invention.
FIG. 3 is a 500-fold magnification of the metallographic structure of the weld center at a weld line energy of 300KJ/cm in the example of the present invention.
FIG. 4 is a 500-fold magnification of the metallographic structure of the weld line at a weld line energy of 250KJ/cm according to an embodiment of the present invention.
FIG. 5 is a 500-fold magnification of the metallographic structure of the weld line at a weld line energy of 300KJ/cm according to an embodiment of the present invention.
FIG. 6 is a 500-fold magnification showing a metallographic structure of a weld heat affected zone at a weld heat input of 250KJ/cm in an example of the present invention.
FIG. 7 is a 500-fold enlargement of a metallographic structure of a weld heat affected zone at a weld heat input of 300KJ/cm in an example of the present invention.
Detailed Description
The steel for a low silicon universal joint cage and the manufacturing method thereof according to the present invention will be further explained and illustrated with reference to the drawings and the specific examples, which, however, should not be construed to unduly limit the technical scope of the present invention.
Example 1
The high-strength boat deck EH36 for high heat input welding of this embodiment, 50mm in thickness, is prepared by melting the following components by mass percent: c: 0.08%, Si: 0.35%, Mn: 1.54%, P: 0.008%, S: 0.003%, Al: 0.005%, Nb: 0.016%, Ni: 0.30%, Ti: 0.015% of Ca, 0.003% of Ca and the balance of Fe and inevitable impurities.
The steps of the method for producing the high-strength boat deck EH36 for high heat input welding of the embodiment are as follows:
(1) smelting: the composite material comprises the following components in percentage by mass: 0.08%, Si: 0.35%, Mn: 1.54%, P: 0.008%, S: 0.003%, Al: 0.005%, Nb: 0.016%, Ni: 0.30%, Ti: smelting 0.015 percent of molten steel with 0.003 percent of Ca in an electric furnace, feeding the molten steel into an LF refining furnace for refining, deoxidizing by using Ti when the oxygen content is 15PPM, and transferring the molten steel into an RH furnace for vacuum degassing treatment when the temperature of the molten steel reaches 1570 ℃; the vacuum degree is 66.6Pa, the vacuum is kept for 20 minutes, the Fe-Ca wire is added to the vacuum degassing treatment for 450m, the soft blowing is carried out for 3 minutes to ensure that the components of the molten steel are uniform, and then the molten steel is poured by a ladle;
(2) continuous casting: the production is carried out by adopting a slab caster with the thickness of 370mm, and the casting temperature is 1540 ℃;
(3) heating: the heating temperature of the continuous casting billet is 1220 ℃ at most, the soaking temperature is 1200 ℃, and the temperature is kept for 3.5 hours;
(4) rolling: rolling by adopting a recrystallization and non-recrystallization two-stage rolling process, wherein the airing thickness is 110mm, the initial rolling temperature of the first stage is 1055 ℃, the final rolling temperature is 970 ℃, and the cumulative reduction rate is 60%; the second stage has the initial rolling temperature of 850 ℃, the final rolling temperature of 820 ℃ and the cumulative reduction rate of 55 percent to obtain a crude steel plate;
(5) water cooling after rolling of the steel plate: after the steel plate is rolled, the steel plate is rapidly cooled by water, a DQ mode is set, the cooling speed is 15 ℃/second, the water quantity is automatically controlled, the steel plate water inlet temperature is 790 ℃, and the steel plate water outlet re-reddening temperature is 580 ℃.
Mechanical properties and metallographic structure of the 50mm steel sheet of this example:
(1) mechanical properties of the board
The yield strength is 410MPa, the tensile strength is 550MPa, and the transverse impact absorption energy KV2 average 258J at the temperature of minus 40 ℃ is.
(2) Mechanical properties of heat affected zone of plate welding
The yield strength is 405MPa, the tensile strength is 540MPa, and the transverse impact absorption energy KV2 is 191J on average at the temperature of minus 40 ℃.
(3) Phase structure
The high-strength boat deck EH36 for large heat input welding has uniform and fine structure and 9.5-grade grain size; the texture coarsening of the steel plate welding heat affected zone is controlled within a certain range, and the grain size is 7.5 grade. The metallographic pictures are shown in fig. 1 and fig. 2.
Example 2
The high-strength ship board EH36 for high heat input welding of the embodiment, which has a thickness of 70mm, is prepared by melting the following components in percentage by mass: c: 0.10%, Si: 0.30%, Mn: 1.55%, P: 0.007%, S: 0.003%, Al: 0.004%, Nb: 0.020%, Ni: 0.28%, Ti: 0.019% of Ca, 0.003% of Ca, and the balance of Fe and inevitable impurities.
The method for producing the high-strength and high-strength ship board EH36 steel plate for high heat input welding of the embodiment comprises the following steps:
(1) smelting: the composite material comprises the following components in percentage by mass: 0.10%, Si: 0.30%, Mn: 1.55%, P: 0.007%, S: 0.003%, Al: 0.004%, Nb: 0.020%, Ni: 0.28%, Ti: smelting 0.019% of molten steel and 0.003% of Ca in an electric furnace, feeding the molten steel into an LF refining furnace for refining, deoxidizing by using Ti when the oxygen content reaches 48PPM, and transferring the molten steel into an RH furnace for vacuum degassing treatment when the temperature of the molten steel reaches 1560 ℃; the vacuum degree is 66.6Pa, the vacuum holding time is 20 minutes, the pure Ca wire is added for 400m after the vacuum degassing treatment, the soft blowing is carried out for 3 minutes to ensure that the components of the molten steel are uniform, and then the ladle is used for pouring.
(2) Continuous casting: the casting is carried out by adopting a slab caster with the thickness of 370mm, and the casting temperature is 1542 ℃.
(3) Heating: the heating temperature of the continuous casting billet is 1240 ℃ at most, the soaking temperature is 1220 ℃, and the temperature is kept for 4 hours;
(4) rolling: rolling by adopting a recrystallization and non-recrystallization two-stage rolling process, wherein the airing thickness is 140mm, the initial rolling temperature of the first stage is 1050 ℃, the final rolling temperature is 960 ℃, and the accumulated reduction rate is 60%; the second stage is that the initial rolling temperature is 840 ℃, the final rolling temperature is 810 ℃, and the cumulative reduction rate is 55 percent to obtain a crude steel plate product;
(5) water cooling after rolling of the steel plate: after the steel plate is rolled, the steel plate is rapidly cooled by water, a DQ mode is set, the cooling speed is 15 ℃/second, the water quantity is automatically controlled, the water inlet temperature of the steel plate is 800 ℃, and the water outlet re-reddening temperature of the steel plate is 600 ℃.
Mechanical properties of the 70mm steel sheet of this example:
(1) mechanical properties of steel sheet
The yield strength is 455MPa, the tensile strength is 585MPa, and the transverse impact absorption energy at-40 ℃ is KV2 average 212J.
(2) Mechanical property of welding heat affected zone of steel plate
The yield strength is 450MPa, the tensile strength is 570MPa, and the transverse impact absorption energy KV2 is 185J on average at-40 ℃.
(3) Phase structure
The high-strength boat deck EH36 for large heat input welding has uniform and fine structure and 9.5-grade grain size; coarsening of the texture of the steel plate welding heat affected zone is controlled within a certain range, and the grain size is 7.5 grade. The metallographic photograph of the steel plate is shown in FIGS. 3 and 4.
Example 3
The high-strength and high-strength ship board EH36 for high heat input welding of the embodiment has a thickness of 100mm, and is prepared by melting the following components in percentage by mass: c: 0.10%, Si: 0.30%, Mn: 1.50%, P: 0.004%, S: 0.003%, Al: 0.004%, Nb: 0.020%, Ni: 0.28%, Ti: 0.019% of Ca, 0.003% of Ca, and the balance of Fe and inevitable impurities.
The method for producing the high-strength and high-strength ship board EH36 steel plate for high heat input welding of the embodiment comprises the following steps:
(1) smelting: the composite material comprises the following components in percentage by mass: 0.10%, Si: 0.30%, Mn: 1.50%, P: 0.004%, S: 0.003%, Al: 0.004%, Nb: 0.020%, Ni: 0.28%, Ti: smelting 0.019% of molten steel and 0.003% of Ca in an electric furnace, feeding the molten steel into an LF refining furnace for refining, deoxidizing by using Ti when the oxygen content is 95PPM, and transferring the molten steel into an RH furnace for vacuum degassing treatment when the temperature of the molten steel reaches 1565 ℃; the vacuum degree is 66.6Pa, the vacuum holding time is 20 minutes, the pure Ca wire is added for 400m after the vacuum degassing treatment, the soft blowing is carried out for 3 minutes to ensure that the components of the molten steel are uniform, and then the ladle is used for pouring.
(2) Continuous casting: the production is carried out by adopting a slab caster with the thickness of 450mm, and the casting temperature is 1542 ℃.
(3) Heating: the heating temperature of the continuous casting billet is 1240 ℃ at most, the soaking temperature is 1220 ℃, and the temperature is kept for 5 hours;
(4) rolling: rolling by adopting a recrystallization and non-recrystallization two-stage rolling process, wherein the airing thickness is 180mm, the initial rolling temperature of the first stage is 1050 ℃, the final rolling temperature is 960 ℃, and the accumulated reduction rate is 60%; the second stage is that the initial rolling temperature is 840 ℃, the final rolling temperature is 810 ℃, and the cumulative reduction rate is 44 percent to obtain a crude steel plate product;
(5) water cooling after rolling of the steel plate: after the steel plate is rolled, the steel plate is rapidly cooled by water, a DQ mode is set, the cooling speed is 15 ℃/second, the water quantity is automatically controlled, the water inlet temperature of the steel plate is 800 ℃, and the water outlet re-reddening temperature of the steel plate is 600 ℃.
Mechanical properties of the 100mm steel sheet of this example:
(1) mechanical properties of steel sheet
The yield strength is 430MPa, the tensile strength is 575MPa, and the transverse impact absorption energy KV2 is 225J on average at-40 ℃.
(2) Mechanical property of welding heat affected zone of steel plate
Yield strength 415MPa, tensile strength 560MPa, and transverse impact absorption energy KV2 average 189J at-40 ℃.
(3) Metallographic structure
The high-strength boat deck EH36 for large heat input welding has uniform and fine structure and 9.5-grade grain size; coarsening of the texture of the steel plate welding heat affected zone is controlled within a certain range, and the grain size is 7.5 grade. The metallographic photograph of the steel plate is shown in FIGS. 5 and 6.
It should be noted that the above examples are only specific embodiments of the present invention, and it is obvious that the present invention is not limited to the above embodiments, but many similar variations are possible as needed. All modifications which would occur to one skilled in the art and which are, therefore, directly derivable or suggested by the disclosure herein are to be included within the scope of the present invention.
Claims (3)
1. A production method of a high-strength EH36 steel plate for high heat input welding is characterized by comprising the following steps:
(1) smelting: the composite material comprises the following components in percentage by mass: 0.06% -0.18%, Si: 0.15-0.50%, Mn: 1.10-1.60%, P is less than or equal to 0.012%, S is less than or equal to 0.003%, Ni: 0.10% -0.40%, Nb: 0.010% -0.030%, Al: less than or equal to 0.010 percent, Ti: 0.010% -0.030%, Ca: smelting 0.002-0.010% of molten steel by an electric furnace or a converter, feeding the molten steel into an LF refining furnace for refining, deoxidizing by using Ti during LF refining, transferring the molten steel into an RH furnace for vacuum degassing treatment when the temperature of the molten steel reaches 1560 +/-10 ℃, adding 400-500 m Fe-Ca wires or 300-400 m pure Ca wires after the vacuum degassing treatment, soft blowing for 3 minutes to ensure that the components of the molten steel are uniform, and then hanging and pouring;
al deoxidation is not used during refining, in the early stage of refining, a weak deoxidation element is used for deoxidation to reduce the content of free oxygen in molten steel to 10-100 ppm, argon is blown greatly to enable S in the molten steel to reach a specified value, meanwhile, most of Al remaining in the molten steel is consumed, the content of Al is less than or equal to 0.0075%, then Ti is added, a certain amount of free oxygen contained in the molten steel is combined with Ti to form fine Ti oxides in the molten steel, the vacuum degree of vacuum degassing treatment is not more than 66.6Pa, and the vacuum retention time is not less than 20 minutes;
(2) continuous casting: the steel is produced by adopting a slab caster with the thickness of 150mm, 200mm, 370mm and 450mm, and the casting temperature is 1535-1545 ℃;
(3) heating: the maximum heating temperature of the continuous casting billet is 1220-1240 ℃, the soaking temperature is 1200-1220 ℃, and the temperature is kept for 3-5 hours;
(4) rolling: rolling by adopting a two-stage rolling process of a recrystallization zone and a non-recrystallization zone, wherein the rolling temperature of the first stage is 930-1100 ℃, the single-pass reduction of the first stage is 10-20%, and the cumulative reduction rate is 40-60%; the rolling temperature of the second stage is 800-880 ℃, the accumulated reduction rate is 40% -60%, and a crude steel plate product is obtained;
(5) water cooling after rolling of the steel plate: after the steel plate is rolled, the steel plate is rapidly cooled by water, a direct quenching mode is set, the cooling speed is 10-20 ℃/s, the water quantity is automatically controlled, the water inlet temperature of the steel plate is 750-800 ℃, and the water outlet re-reddening temperature of the steel plate is 550-650 ℃.
2. The method for producing the high-strength EH36 steel plate for large heat input welding according to claim 1, wherein the thickness of the intermediate airing steel in the step (4) is 2 to 3 times of the thickness of the finished plate, the initial rolling temperature of the first stage rolling is 1050 to 1100 ℃, and the final rolling temperature is 930 to 950 ℃; the rolling temperature of the second stage is 840-880 ℃, and the finishing temperature is 800-820 ℃.
3. The method of producing a high strength EH36 steel sheet for high heat input welding according to claim 1, wherein the maximum allowable weld input line energy of the steel sheet is 300 kJ/cm.
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