CN109321851B - 690 MPa-grade yield strength steel plate capable of bearing high heat input welding and manufacturing method thereof - Google Patents
690 MPa-grade yield strength steel plate capable of bearing high heat input welding and manufacturing method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of low-alloy high-strength steel, and particularly relates to a steel plate with yield strength of 690MPa and capable of bearing high heat input welding and a manufacturing method thereof. The steel sheet comprises 0.01-0.04% of C, 0.1-0.3% of Si, 1.7-2.2% of Mn, 0.01-0.05% of Nb, 0.01-0.05% of V, 0.005-0.025% of Ti, 0.001-0.008% of P, 0.001-0.005% of S, 0.05-0.5% of Cu, 0.05-0.5% of Ni, 0.05-0.5% of Cr, 0.05-0.5% of Mo, 0.0005-0.0025% of B, 0.001-0.005% of N, 0.00002-0.0002% of H, 0.001-0.005% of O, 0.001-0.015% of Al, one of Mg and Ca, and the balance of Fe; in the inclusions with the size of 0.2-3 mu m in the steel plate, the content of Ti-Mg-O or Ti-Ca-O composite inclusions is more than 10%, and the average content of Ti is 1-50%; the number of inclusions with the size of more than 3 mu m in the steel plate is less than or equal to 120 inclusions/mm3. An LD-RH-LF-RH smelting process is adopted, when the oxygen content of the molten steel is 150-300 ppm,adding Ti and Mg or Ca; two-stage rolling and cooling control is adopted. The steel plate has excellent strength and toughness, and can bear large-line energy welding of 100-200 kJ/cm.
Description
Technical Field
The invention belongs to the technical field of low-alloy high-strength steel, and particularly relates to a steel plate with yield strength of 690MPa and capable of bearing high heat input welding and a manufacturing method thereof.
Background
The medium plate steel mostly relates to the welding process in engineering application, and welding parameters need to be strictly controlled in order to ensure the quality of a welding joint. The conventional welding heat input is below 50kJ/cm, the heat input is increased, the welding efficiency can be improved, and the engineering manufacturing period is shortened. Especially for thick steel plates, the conventional welding method needs multi-pass welding forming and complicated auxiliary work before welding and between layers, but the large heat input welding method can be used for one-pass forming, so that the production efficiency is improved by times or tens of times. Therefore, in various engineering fields, the manufacture of large-scale steel welding structures tends to adopt a high heat input welding method, so that the manufacturing cost is obviously reduced and the production efficiency is improved.
At present, extensive research is carried out on the production process of medium-strength-level large heat input welding steel with yield strength of 300-500 MPa, but the production of 690 MPa-level high-strength steel for large heat input welding still has difficulty, and a production process technology with strong feasibility, reliable performance and low alloy cost needs to be developed urgently.
The invention patent with the publication number of CN102041459A discloses a HT690 steel plate capable of being welded by large heat input and a manufacturing method thereof, which is characterized in that a low-C-high-Mn- (Nb + V + B) microalloying-ultramicro Ti processing component system is adopted, acid-soluble Al in steel is properly improved, the ratio relation among elements is controlled, a TMCP + tempering process is optimized, and fine tempered bainite is formed, has large heat input welding performance, but the yield strength is less than 690 MPa. The invention patent with the publication number of CN101165202A discloses a high-strength steel with high toughness of a welding heat affected zone and a manufacturing method thereof, and is characterized in that an ultra-low carbon design is adopted, Mn is used as a main element, Cr and Ni are used as auxiliary elements, and a controlled rolling and controlled cooling process is combined, so that the toughness of the high-strength steel and the welding heat affected zone is improved, the yield strength reaches more than 690MPa, and the high-strength steel is suitable for conventional linear energy welding of 25-30 kJ/cm. The invention patent with the publication number of CN102312173A discloses steel with the tensile strength of 700MPa for a large heat input welding structure and a manufacturing method thereof, which are characterized in that oxides such as Ti, Zr and the like are formed through reasonable design of components, quenching and tempering are not needed, a TMCP process is adopted, the large heat input welding of 30-100 kJ/cm can be realized, and the yield strength is less than 690 MPa. The invention patent with the publication number of CN102839330A discloses a thick plate for 800 MPa-grade high-strength high heat input welding, which is characterized in that on the basis of low-carbon steel components, the Ni content is increased, meanwhile, a proper amount of alloy elements such as Cr, Mo and the like are added, the thickness of the steel plate is within 30mm, and the thick plate is suitable for welding heat input of 40-100 kJ/cm. The invention patent with publication number CN1676656A discloses an ultrahigh strength thick steel plate capable of being welded by large heat input and a manufacturing method thereof, which is characterized in that the invention adopts alloy design with lower carbon equivalent, and realizes the organic unification of high strength, high toughness and weldability by asynchronous rolling, strain relaxation and direct quenching cooling in an austenite non-recrystallization zone, and realizes the large heat input welding by reducing the dosage of alloy elements.
In the prior art, the steel plate can realize large heat input welding through alloy design and smelting production process control, but the strength level can not meet the requirement; or a large amount of noble alloy element Ni is needed to be added to improve the toughness and the welding performance, so that the alloy cost is increased; when the low alloy composition design is adopted, although the strength requirement can be met, the large heat input welding can not be realized; or special processing methods are needed to reduce alloy elements and improve strength and weldability. Therefore, the prior art still cannot meet the urgent need of 690 MPa-grade high-strength steel capable of bearing 100-200 kJ/cm high heat input welding.
Disclosure of Invention
The invention aims to provide a 690 MPa-grade yield strength steel plate capable of bearing high heat input welding and a manufacturing method thereof, which solve the problem of low high heat input welding performance of a high-strength steel plate and realize the remarkable improvement of comprehensive performance of toughness and high heat input welding performance.
The invention adopts the following technical scheme:
a690 MPa-grade yield strength steel plate capable of bearing high heat input welding comprises the following chemical components in percentage by mass: 0.01 to 0.04% of C, 0.1 to 0.3% of Si, 1.7 to 2.2% of Mn, 0.01 to 0.05% of Nb, 0.01 to 0.05% of V, 0.005 to 0.025% of Ti, 0.001 to 0.008% of P, 0.001 to 0.005% of S, 0.05 to 0.5% of Cu, 0.05 to 0.5% of Ni, 0.05 to 0.5% of Cr, 0.05 to 0.5% of Mo, 0.0005 to 0.0025% of B, 0.001 to 0.005% of N, 0.00002 to 0.0002% of H, 0.001 to 0.005% of O, 0.001 to 0.015% of Al, 0.0005 to 0.005% of Mg, 0.0005 to 0.005% of Ca, and the balance Fe; in the inclusions with the size of 0.2-3 mu m in the steel plate, the number of Ti-Mg-O or Ti-Ca-O composite inclusions accounts for more than 10%.
The steel plate with the yield strength of 690MPa and capable of bearing high heat input welding contains 1-50% of Ti in the Ti-Mg-O or Ti-Ca-O inclusion on average.
The 690 MPa-grade yield strength steel plate capable of bearing high heat input welding preferably contains 10-30% of Ti in Ti-Mg-O or Ti-Ca-O inclusions on average.
The steel plate with the yield strength of 690MPa and the capability of bearing high heat input welding has the steel plate that the number of inclusions with the size of more than 3 mu m is less than or equal to 120 inclusions/mm3。
The 690 MPa-grade yield strength steel plate capable of bearing high heat input welding is preferably selected, the number of inclusions with the size of more than 3 mu m in the steel plate is 10-100/mm3。
The steel plate with the yield strength of 690MPa and the capability of bearing high heat input welding has the thickness of 12-50 mm, the yield strength of more than or equal to 690MPa, and the impact toughness of a base metal and a heat affected zone at minus 40 ℃ of more than or equal to 70J under the welding heat input of 100-200 kJ/cm.
The manufacturing method of the 690 MPa-grade yield strength steel plate capable of bearing high heat input welding comprises the steps of adopting an LD-RH-LF-RH smelting process for molten steel, controlling the end point oxygen content of an LD converter to be 500-800 ppm, controlling the carbon content to be 0.025-0.06%, and controlling the phosphorus content to be 0.001 ℃: E0.008 percent; performing vacuum decarburization treatment by RH, and controlling the carbon content in the molten steel to be 0.001-0.01 wt% and the oxygen content to be 150-300 ppm; LF refining is carried out after RH decarburization treatment is finished, and the sulfur content of molten steel is controlled to be 0.001-0.005%; performing RH vacuum circulation degassing treatment after LF refining is finished, wherein the degassing time is 10-20 min under 100 Pa; when the oxygen content of molten steel in refining is 150-300 ppm, adding Ti and one of Mg or Ca in an alloy block or wire feeding mode, wherein the interval time between the Ti and the Mg or Ca is 15-30 min; after deoxidation, argon is blown and the mixture is stirred for 10 to 20min, so that the number of inclusions with the diameter of more than 3 mu m in the steel is 10 to 100 per mm3(ii) a Adjusting the content of other alloy elements according to the component requirements of the steel plate, and casting molten steel with qualified components into a continuous casting billet; heating the continuous casting blank to 1150-1250 ℃, preserving heat for 100-200 min, and controlling rolling in two stages of an austenite recrystallization zone and a non-recrystallization zone, wherein the accumulated reduction rate of the non-recrystallization zone is more than or equal to 60%; and (3) watering and cooling the rolled steel plate at the cooling speed of 10-30 ℃/s and the final cooling temperature of 350-550 ℃.
The manufacturing method of the 690 MPa-grade yield strength steel plate capable of bearing high heat input welding comprises the step of tempering or quenching and tempering the steel plate.
The manufacturing method of the 690 MPa-grade yield strength steel plate capable of bearing high heat input welding preferably has the steel plate thickness of 15-35 mm, the yield strength of 700-800 MPa, and the base metal and the heat affected zone have the impact toughness of 100-200J at minus 40 ℃ under the welding heat input of 100-200 kJ/cm.
The design idea of the invention is as follows:
aiming at the problem that high-strength or ultrahigh-strength steel is difficult to perform large-heat input welding, the invention adopts the means of ultra-low carbon design, alloy component optimization, high-cleanliness smelting and special inclusion control, overcomes the defects of the prior art and realizes the remarkable improvement of the comprehensive performance of the high-strength steel plate. By RH decarburization treatment, the number and size of high-carbon M/A islands in the HAZ of large heat input welding are obviously reduced, and brittle fracture is reduced; when higher Mn is adopted and alloy elements such as Nb, V, Cu and the like are controlled within the range, the strength and toughness performance and the high heat input welding performance of the steel plate can be comprehensively improved; by controlling the smelting deoxidation process, special inclusion distribution is formed, HAZ structure refinement is promoted, low-temperature toughness is improved, and adverse effects of impurity elements and large-size inclusions are reduced; under the condition of the components, the rolling and heat treatment process ensures the excellent comprehensive strength and toughness of the steel plate.
The invention has the advantages and beneficial effects that:
1. the invention realizes high strength, high toughness and large heat input welding performance by low carbon component design and special inclusion control and combining the optimization of smelting and rolling cooling processes. The low-carbon composition design avoids the generation of embrittlement structures such as MA component causing embrittlement of a welding heat affected zone, the strength and toughness of the steel plate are improved by adopting an optimized rolling cooling process, and precious alloy elements are not added in a large amount. By improving the key smelting process and controlling the type and distribution of the inclusions, the texture refinement of the large heat input welding heat affected zone is promoted, and the large heat input welding performance is improved.
2. The technical scheme provided by the invention has the advantages of strong feasibility and obvious effect, and can meet the urgent need of 690 MPa-grade high-strength steel capable of bearing large-heat input welding of 100-200 kJ/cm.
Drawings
FIGS. 1-2 are typical microstructures of the 200kJ/cm weld heat affected zone of example steels. Wherein FIG. 1 is an optical microstructure; FIG. 2 shows SEM structure.
Detailed Description
The present invention will be explained in further detail below by way of examples and figures.
Example 1
In the embodiment, the steel plate with the yield strength of 690MPa and capable of bearing high heat input welding comprises the following chemical components in percentage by mass: 0.01% of C, 0.2% of Si, 1.9% of Mn, 0.02% of Nb, 0.05% of V, 0.005% of Ti, 0.003% of P, 0.002% of S, 0.05% of Cu, 0.5% of Ni, 0.05% of Cr, 0.5% of Mo, 0.0005% of B, 0.001% of N, 0.0002% of H, 0.005% of O, 0.01% of Al, 0.001% of Mg and the balance of Fe; in the inclusions with the size of 0.2-3 mu m in the steel plate, the number of Ti-Mg-O composite inclusions accounts for 50 percent; the Ti-Mg-O inclusion contains 15% of Ti on average according to mass fraction; the number of inclusions with a size of 3 μm or more in the steel sheet is 30 to 50 inclusions/mm3。
The steel plateThe manufacturing method of (1): the LD converter smelting end point oxygen content is 650ppm, the carbon content is 0.05 percent, and the phosphorus content is 0.003 percent; RH vacuum decarburization is carried out, the carbon content in the molten steel is 0.008 percent, and the oxygen content is 150 ppm; LF refining is carried out after RH is finished, and the sulfur content of the molten steel is 0.002%; performing RH vacuum degassing treatment after LF refining is finished, wherein the degassing time is below 80Pa for 10 min; adding Ti and Mg alloy blocks when the oxygen content is 150ppm during refining, wherein the interval time between the Ti and Mg alloy blocks is 15 min; blowing argon for 10min after deoxidation, wherein the number of inclusions with the diameter of more than 3 mu m in the steel is 30-60/mm3(ii) a Adjusting the content of other alloy elements such as Nb, V, Cu, Ni and the like according to the component requirements of the steel plate, and casting molten steel with qualified components into a continuous casting billet; heating the continuous casting slab to 1150 ℃, preserving heat for 200min, and controlling rolling in two stages of an austenite recrystallization zone and a non-recrystallization zone, wherein the accumulated reduction rate of the non-recrystallization zone is 70%; and (3) watering and cooling the rolled steel plate at the cooling speed of 20 ℃/s and the final cooling temperature of 500 ℃.
The thickness of the steel plate is 20mm, the yield strength is 750MPa, the impact toughness at minus 40 ℃ is 180J, and the impact toughness at minus 40 ℃ of a heat affected zone is 70-150J under the welding line energy of 100-200 kJ/cm.
Example 2
In the embodiment, the steel plate with the yield strength of 690MPa and capable of bearing high heat input welding comprises the following chemical components in percentage by mass: 0.04% of C, 0.1% of Si, 1.7% of Mn, 0.01% of Nb, 0.02% of V, 0.015% of Ti, 0.005% of P, 0.005% of S, 0.5% of Cu, 0.4% of Ni, 0.45% of Cr, 0.15% of Mo, 0.0025% of B, 0.005% of N, 0.0001% of H, 0.004% of O, 0.015% of Al, 0.001% of Ca and the balance of Fe; in the inclusions with the size of 0.2-3 mu m in the steel plate, the number of Ti-Ca-O composite inclusions accounts for 30 percent; the Ti-Ca-O inclusion contains 25% of Ti on average according to mass fraction; the number of inclusions with a size of 3 μm or more in the steel sheet is 10 to 30 inclusions/mm3。
The method for manufacturing the steel plate comprises the following steps: the LD converter smelting end point oxygen content is 710ppm, the carbon content is 0.04 percent, and the phosphorus content is 0.005 percent; RH vacuum decarburization is carried out, the carbon content in the molten steel is 0.004%, and the oxygen content is 250 ppm; LF refining is carried out after RH is finished, and the sulfur content of molten steel is 0.005%; performing RH vacuum degassing treatment after LF refining is finished, wherein the degassing time is below 60Pa for 15 min; adding Ti and Ca alloy wires at a spacing of 280ppm of oxygen during refiningThe time is 25 min; blowing argon for 20min after deoxidation, wherein the number of inclusions with the diameter of more than 3 mu m in the steel is 10-30/mm3(ii) a Adjusting the content of other alloy elements such as Nb, V, Cu, Ni and the like according to the component requirements of the steel plate, and casting molten steel with qualified components into a continuous casting billet; heating the continuous casting blank to 1250 ℃, preserving heat for 100min, and controlling rolling in two stages of an austenite recrystallization zone and a non-recrystallization zone, wherein the cumulative reduction rate of the non-recrystallization zone is 60%; watering and cooling the rolled steel plate at the cooling speed of 15 ℃/s and the final cooling temperature of 450 ℃; and (3) carrying out quenching and tempering heat treatment on the steel plate, wherein the quenching heating temperature is 900 ℃, the heat preservation time is 30min, the tempering temperature is 600 ℃, and the heat preservation time is 50 min.
The thickness of the steel plate is 50mm, the yield strength is 690MPa, the impact toughness at minus 40 ℃ is 200J, and the impact toughness at minus 40 ℃ of a heat affected zone is 70-150J under the welding line energy of 100-200 kJ/cm.
As shown in figures 1-2, a typical microstructure of a welding heat affected zone of 200kJ/cm of the example steel is an acicular ferrite-type structure, the size is uniformly refined, and the low-temperature impact toughness and the strength are remarkably improved.
The embodiment result shows that the steel plate has high strength and toughness, excellent comprehensive performance of high heat input weldability and can bear the high heat input welding of 100-200 kJ/cm.
Claims (2)
1. A manufacturing method of a 690 MPa-grade yield strength steel plate capable of bearing high heat input welding is characterized in that the 690 MPa-grade yield strength steel plate capable of bearing high heat input welding comprises the following chemical components in percentage by mass: 0.01% of C, 0.2% of Si, 1.9% of Mn, 0.02% of Nb, 0.05% of V, 0.005% of Ti, 0.003% of P, 0.002% of S, 0.05% of Cu, 0.5% of Ni0.5% of Cr, 0.5% of Mo, 0.0005% of B, 0.001% of N, 0.0002% of H, 0.005% of O, 0.01% of Al, 0.001% of Mg and the balance of Fe; in the inclusions with the size of 0.2-3 mu m in the steel plate, the number of Ti-Mg-O composite inclusions accounts for 50 percent; the Ti-Mg-O inclusion contains 15 percent of Ti on average according to mass fraction; the number of inclusions with a size of 3 μm or more in the steel sheet is 30 to 50 inclusions/mm3；
The method for manufacturing the steel plate comprises the following steps: the LD converter smelting end point oxygen content is 650ppm, the carbon content is 0.05 percent, and the phosphorus content is 0.003 percent; carrying out RHVacuum decarburization, wherein the carbon content in the molten steel is 0.008 percent, and the oxygen content is 150 ppm; LF refining is carried out after RH is finished, and the sulfur content of the molten steel is 0.002%; performing RH vacuum degassing treatment after LF refining is finished, wherein the degassing time is below 80Pa for 10 min; adding Ti and Mg alloy blocks when the oxygen content is 150ppm during refining, wherein the interval time between the Ti and Mg alloy blocks is 15 min; blowing argon for 10min after deoxidation, wherein the number of inclusions with the diameter of more than 3 mu m in the steel is 30-60/mm3(ii) a Adjusting the contents of other alloy elements such as Nb, V, Cu and Ni according to the component requirements of the steel plate, and casting molten steel with qualified components into a continuous casting billet; heating the continuous casting slab to 1150 ℃, preserving heat for 200min, and controlling rolling in two stages of an austenite recrystallization zone and a non-recrystallization zone, wherein the accumulated reduction rate of the non-recrystallization zone is 70%; watering and cooling the rolled steel plate at the cooling speed of 20 ℃/s and the final cooling temperature of 500 ℃;
the thickness of the steel plate is 20mm, the yield strength is 750MPa, the impact toughness at minus 40 ℃ is 180J, and the impact toughness at minus 40 ℃ of a heat affected zone is 70-150J under the welding line energy of 100-200 kJ/cm.
2. A manufacturing method of a 690 MPa-grade yield strength steel plate capable of bearing high heat input welding is characterized in that the 690 MPa-grade yield strength steel plate capable of bearing high heat input welding comprises the following chemical components in percentage by mass: 0.04% of C, 0.1% of Si, 1.7% of Mn, 0.01% of Nb, 0.02% of V, 0.015% of Ti, 0.005% of P, 0.005% of S, 0.5% of Cu, 0.4% of Ni0.4%, 0.45% of Cr, 0.15% of Mo, 0.0025% of B, 0.005% of N, 0.0001% of H, 0.004% of O, 0.015% of Al, 0.001% of Ca and the balance of Fe; in the inclusions with the size of 0.2-3 mu m in the steel plate, the number of Ti-Ca-O composite inclusions accounts for 30 percent; the Ti-Ca-O inclusion contains 25 percent of Ti on average according to mass fraction; the number of inclusions with a size of 3 μm or more in the steel sheet is 10 to 30 inclusions/mm3；
The method for manufacturing the steel plate comprises the following steps: the LD converter smelting end point oxygen content is 710ppm, the carbon content is 0.04 percent, and the phosphorus content is 0.005 percent; RH vacuum decarburization is carried out, the carbon content in the molten steel is 0.004%, and the oxygen content is 250 ppm; LF refining is carried out after RH is finished, and the sulfur content of molten steel is 0.005%; performing RH vacuum degassing treatment after LF refining is finished, wherein the degassing time is below 60Pa for 15 min; adding Ti and Ca alloy wires when the oxygen content is 280ppm in refining, wherein the interval time between the Ti and Ca alloy wires is 25 min; after deoxidationArgon blowing is carried out for 20min, and the number of inclusions with the diameter of more than 3 mu m in the steel is 10-30/mm3(ii) a Adjusting the contents of other alloy elements such as Nb, V, Cu and Ni according to the component requirements of the steel plate, and casting molten steel with qualified components into a continuous casting billet; heating the continuous casting blank to 1250 ℃, preserving heat for 100min, and controlling rolling in two stages of an austenite recrystallization zone and a non-recrystallization zone, wherein the cumulative reduction rate of the non-recrystallization zone is 60%; watering and cooling the rolled steel plate at the cooling speed of 15 ℃/s and the final cooling temperature of 450 ℃; carrying out quenching and tempering heat treatment on the steel plate, wherein the quenching heating temperature is 900 ℃, the heat preservation time is 30min, the tempering temperature is 600 ℃, and the heat preservation time is 50 min;
the thickness of the steel plate is 50mm, the yield strength is 690MPa, the impact toughness at minus 40 ℃ is 200J, and the impact toughness at minus 40 ℃ of a heat affected zone is 70-150J under the welding line energy of 100-200 kJ/cm.
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| CN101760695A (en) * | 2008-12-22 | 2010-06-30 | 株式会社神户制钢所 | Thick steel plate |
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