CN112746224A - 690 MPa-grade steel plate for ocean engineering and manufacturing method thereof - Google Patents
690 MPa-grade steel plate for ocean engineering and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a 690 MPa-grade steel plate for ocean engineering and a manufacturing method thereof, belongs to the technical field of ocean engineering steel, and solves the problem that the 690 MPa-grade steel plate for ocean engineering in the prior art is poor in weldability. The steel plate comprises the following chemical components in percentage by mass: c: 0.02% -0.05%, Si: 0.05-0.10%, Mn: 0.5% -2.0%, P: not more than 0.008 percent, not more than 0.005 percent of S, Als: 0.01% -0.051%, Ni: 1.0-5.0%, Cr: 0.2% -1.5%, Mo: 0.2% -1.5%, Cu: 0.5% -2.5%, Ti: 0.005% -0.05%, V: 0.005% -0.05%, B: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities. The steel plate has good obdurability and is easy to weld.
Description
Technical Field
The invention belongs to the technical field of steel for ocean engineering, and particularly relates to a 690 MPa-grade steel plate for ocean engineering and a manufacturing method thereof.
Background
At present, with the increase of the demand of marine exploration, the manufacturing industry of ships and marine engineering equipment is continuously developed, the technical content is continuously improved, and the industry of ships and marine engineering equipment enters a rapid development period. In view of development trend, the global ocean engineering equipment manufacturing industry will develop towards large-scale and diversification, wherein large-scale is also the trend of global low-carbon economy development, and large-scale refers to large-scale development of various indexes including deck, platform main scale, variable load, load capacity, material storage capacity and the like. The large-scale platform requires higher performance of the steel plate, and requires high strength and high toughness on the one hand and good weldability on the other hand. At present, 690 MPa-level structural steel for ocean engineering is mainly delivered in a TMCP state, and has the problems of narrow production process window, preheating for welding in winter especially in a low-temperature environment, even after-welding heating, incapability of ensuring welding quality, high construction cost and the like. In addition, some enterprises are limited by production equipment, and the width of the produced steel plate is small, such as the width is less than 2m and the length is less than 6m, so that the defects of more welding seams, large welding deformation and the like are brought to actual construction. Therefore, designing and developing a 690 MPa-grade ultra-wide and ultra-long easy-to-weld steel plate for large ocean engineering equipment has very important significance in reducing cost, improving equipment construction efficiency, improving structural reliability and the like.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a 690MPa grade steel plate for ocean engineering and a manufacturing method thereof, so as to solve the problem of poor weldability of the 690MPa grade steel plate for ocean engineering in the prior art.
The purpose of the invention is mainly realized by the following technical scheme:
on one hand, the invention provides a 690 MPa-grade steel plate for ocean engineering, which comprises the following chemical components in percentage by mass: c: 0.02% -0.05%, Si: 0.05-0.10%, Mn: 0.5-2.0%, P is less than or equal to 0.008%, S is less than or equal to 0.005%, Als: 0.01% -0.051%, Ni: 1.0-5.0%, Cr: 0.2% -1.5%, Mo: 0.2% -1.5%, Cu: 0.5% -2.5%, Ti: 0.005% -0.05%, V: 0.005% -0.05%, B: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities.
Further, the carbon equivalent Ceq of the 690 MPa-grade steel plate for ocean engineering is less than or equal to 0.65 percent.
Further, the 690MPa grade steel plate for ocean engineering comprises the following chemical components in percentage by mass: c: 0.025% -0.049%, Si: 0.03% -0.09%, Mn: 0.7-0.8%, P is less than or equal to 0.008%, S is less than or equal to 0.005%, Als: 0.028% -0.051%, Ni: 1.76% -2.57%, Cr: 0.35-0.62%, Mo: 0.38% -0.54%, Cu: 1.2% -1.35%, Ti: 0.01% -0.04%, V: 0.02% -0.05%, B: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities.
Further, the structure of the 690 MPa-grade steel plate for ocean engineering is an ultra-low carbon tempered martensite + multi-element nano composite precipitated phase.
On the other hand, the invention also provides a manufacturing method of the 690 MPa-grade steel plate for ocean engineering, which comprises the following steps:
step 1: smelting molten steel by adopting a converter according to component design, strictly controlling the content of impurity elements in the steel, and continuously casting the steel into a billet;
step 2: heating the steel billet at low temperature and preserving heat for homogenization treatment;
and step 3: removing phosphorus from the steel billet after the steel billet is taken out of the furnace by using high-pressure water, and rolling the steel plate in a wide and thick plate rolling mill, wherein the initial rolling temperature of rough rolling is not lower than 1000 ℃, and the final rolling temperature is 750-860 ℃; after rolling, water cooling is carried out, and air cooling is carried out after the water cooling is carried out to 500-650 ℃;
and 4, step 4: and quenching and high-temperature tempering the rolled steel plate, and then cooling the steel plate to room temperature by water to obtain a finished steel plate.
Furthermore, in the step 1, the superheat degree of casting is controlled to be less than 15 ℃, and the withdrawal speed is controlled to be 0.7-1.1 m/min.
Further, in the step 2, the temperature for heating the steel billet at the low temperature is 1000-1160 ℃, and the heat preservation time is 1.5-3 h.
Further, in the step 3, the single deformation amount in the rolling process is controlled to be more than 15%.
Further, in the step 4, the quenching process of the steel plate comprises the following steps: heating the steel plate to an austenitizing temperature T1, preserving heat, and cooling to room temperature by water after preserving heat; wherein the austenitizing temperature T1 is 860-920 ℃, the heat preservation time and the quenching roller speed are respectively as follows according to the thickness T:
6-16mm steel plate: the furnace time is (t +30) min; the quenching roller speed is 15-22 m/min;
17-35mm steel plate: the furnace time is (t +40) min; the quenching roller speed is 10-14 m/min;
36-50mm steel plate: the furnace time is (t +50) min; the quenching roller speed is 5-9 m/min;
51-80mm steel plate: the furnace time is (t +60) min; the quenching roller speed is 1-4 m/min.
Further, in the step 4, the high-temperature tempering process of the steel plate comprises the following steps: the tempering temperature is 630-: (6-7). times.t.
Compared with the prior art, the invention can at least realize one of the following technical effects:
1) according to the invention, the mass percentages of C, Cr, Ni, Mn, Cu and other elements in the steel are accurately controlled, and the excellent mechanical properties of the steel plate are ensured by adopting the design of ultralow carbon and low carbon equivalent, and meanwhile, the weldability of the steel plate is ensured.
2) The invention ensures that the steel structure is ultra-low carbon tempered martensite and multi-element nano composite precipitated phase by adopting a special quenching and tempering heat treatment technology, and the granularity of the multi-element nano composite precipitated phase is less than 20nm, thereby ensuring the obdurability of the steel. Ensuring that the yield strength Rp0.2 is more than or equal to 690MPa (e.g. 710-2The impact fracture fiber rate FA% at-40 ℃ is more than or equal to 150J.
3) The invention adopts the wide and thick plate rolling mill to ensure the super-wide and super-long size of the steel plate, is applied to the construction of large ocean engineering equipment, can effectively reduce welding seams and welding preheating, thereby greatly reducing the construction cost of the equipment and shortening the construction period.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a cross-sectional profile of a non-preheated weld specimen of the steel sheet of example 2 (24mm steel sheet);
FIG. 2 is a steel plate of example 2 with-40 ℃ impact fracture morphology (24mm steel plate);
FIG. 3 is a metallographic structure diagram of a steel sheet according to example 2;
FIG. 4 shows the multi-component nanocomposite precipitates in the metallographic structure of the steel sheet of example 2.
Detailed Description
Hereinafter, a 690MPa grade steel plate for ocean engineering and a method for manufacturing the same will be described in further detail with reference to specific examples, which are provided for comparison and explanation purposes only, and the present invention is not limited to these examples.
The 690MPa grade steel plate for ocean engineering comprises the following alloy components in percentage by mass: c: 0.02% -0.05%, Si: 0.05-0.10%, Mn: 0.5% -2.0%, P: not more than 0.008 percent, not more than 0.005 percent of S, Als: 0.01% -0.051%, Ni: 1.0-5.0%, Cr: 0.2% -1.5%, Mo: 0.2% -1.5%, Cu: 0.5% -2.5%, Ti: 0.005% -0.05%, V: 0.005% -0.05%, B: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities. Wherein the carbon equivalent Ceq of the steel plate is less than or equal to 0.65 percent (C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15).
The function and amount of the components contained in the present invention are specifically described below:
c: has obvious solid solution strengthening effect and can improve the hardenability of the steel, but the increase of the content of C in the steel is very unfavorable for the low-temperature toughness and weldability of the steel. Therefore, the invention adopts the ultra-low carbon design, and the content of C is controlled to be 0.02-0.05%.
Si: one of deoxidizing elements in the steel, and simultaneously, silicon is also a non-carbide forming element, exists in a steel matrix in a solid solution form, has a certain solid solution strengthening effect, but excessive silicon is unfavorable for the low-temperature toughness of the steel, the welding cold crack and hot crack sensitivity of the steel are increased, and the Si content is controlled to be 0.05-0.10%.
Mn: the hardenability of the steel can be obviously improved, and meanwhile, the steel has a certain solid solution strengthening effect, but when the content of Mn is too high, the corrosion resistance of the steel is reduced, and coarse M/A islands are easily formed in a welding heat affected zone, so that the low-temperature toughness of the welding heat affected zone is obviously reduced. The Mn content of the invention is controlled between 0.5 percent and 2.0 percent.
P and S: the impurity elements in the steel are very unfavorable for the performance of the steel, particularly the low-temperature toughness, and the content of the impurity elements in the steel is strictly controlled and is not higher than 0.008 percent and 0.005 percent respectively.
And Als: is a strong deoxidizing element, can be combined with N to form AlN, and has the functions of preventing the aging brittleness of steel and refining crystal grains. The Als content is controlled to be 0.01-0.051 percent.
Ni: the Ni is a key element of the invention, on one hand, the Ni can improve the hardenability and the low-temperature toughness of the steel, is an important element for forming reverse transformation austenite, and has a certain solid solution strengthening function; secondly, the surface hot-embrittlement phenomenon caused by the addition of Cu can be suppressed by the addition of Ni, and thirdly, Ni and Cu can be synergistically precipitated during the temper aging process, and coarsening of a Cu-rich phase is suppressed, thereby enhancing the Cu precipitation strengthening effect. Considering the economic cost of steel, the Ni content is controlled to be 1.0-5.0 percent in the invention.
Cr: the hardenability of the steel can be obviously improved, and meanwhile, Cr can form a compact oxidation film, so that the corrosion resistance of the steel can be obviously improved. The Cr content of the invention is controlled between 0.2 percent and 1.5 percent.
Mo: the hardenability of the steel can be obviously improved, a certain solid solution strengthening effect is achieved, meanwhile, the tempering stability can be improved by Mo, and the tempering brittleness is obviously reduced. The content of Mo in the invention is controlled to be 0.2-1.5%.
Cu: after solid solution, the obvious precipitation strengthening effect is generated in a nanometer precipitation form in the tempering and aging process, the strength loss caused by C reduction can be compensated, and meanwhile, the seawater corrosion resistance of the steel can be improved by Cu. In order to ensure that the steel has certain strength, the content of Cu is controlled to be 0.5-2.5 percent.
Ti: the strong carbonitride forming element, trace Ti can be combined with N in steel to form TiN, thereby preventing austenite grains from growing in soaking and also preventing austenite grains from growing in a welding heat affected zone, and improving weldability. In the invention, the Ti content is controlled to be 0.005-0.05%.
V: carbide forming elements have strong bonding capacity with carbon, form stable VC, can refine grains and improve the strength and the tempering stability of steel, but the low-temperature toughness of the material is damaged due to the fact that the content of V is too high. In the invention, the content of V is controlled to be 0.005-0.05%.
B: the solubility in steel is small, and the hardenability of the material is obviously improved, but the addition of too much can cause grain boundary embrittlement, and is not favorable for weldability and low-temperature toughness. In the invention, the content of B is not more than 0.008%.
In order to further improve the comprehensive performance of the 690MPa grade steel plate for ocean engineering, the composition of the steel plate can be further adjusted. Illustratively, the composition comprises the following components in percentage by mass: c: 0.025% -0.049%, Si: 0.03% -0.09%, Mn: 0.7% -0.8%, P: not more than 0.008 percent, not more than 0.005 percent of S, Als: 0.028% -0.051%, Ni: 1.76% -2.57%, Cr: 0.35-0.62%, Mo: 0.38% -0.54%, Cu: 1.2% -1.35%, Ti: 0.01% -0.04%, V: 0.02% -0.05%, B: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities. Wherein the carbon equivalent Ceq of the steel plate is 0.544-0.648%.
Specifically, the 690MPa grade steel plate for ocean engineering has the thickness of 6-80mm, the width of not less than 3.9m and the length of not less than 16 m.
Specifically, the 690MPa grade steel plate for ocean engineering has low cold crack sensitivity, and can realize non-preheating welding at 0 ℃.
A manufacturing method of a 690 MPa-grade steel plate for ocean engineering comprises the following steps:
step 1: according to the component design, smelting molten steel by adopting a converter, strictly controlling the content of impurity elements in the steel, continuously casting the steel into a billet, and reducing the center segregation of a continuous casting billet by adopting a soft reduction technology or an electromagnetic stirring technology;
step 2: heating the steel billet at low temperature and preserving heat for homogenization treatment;
and step 3: removing phosphorus from the steel billet after the steel billet is taken out of the furnace by using high-pressure water, and rolling the steel plate in a wide and thick plate rolling mill, wherein the initial rolling temperature of rough rolling is not lower than 1000 ℃, and the final rolling temperature is 750-860 ℃; after rolling, water cooling is carried out, and air cooling is carried out after the water cooling is carried out to 500-650 ℃;
and 4, step 4: and quenching and high-temperature tempering the rolled steel plate, and then cooling the steel plate to room temperature by water to obtain a finished steel plate.
In step 1, in order to reduce segregation of elements such as C, Mn, and S in the slab, the degree of superheat of casting is controlled to be less than 15 ℃, and the withdrawal speed is controlled to be 0.7-1.1 m/min.
Specifically, in the step 2, the temperature for low-temperature heating of the steel billet is 1000-1160 ℃, and the heat preservation time is controlled to be 1.5-3 h. The purpose of low-temperature heating is to reduce the scale on the surface of the steel plate, improve the surface quality of the steel plate and prevent the austenite grains from being coarsened too much.
Specifically, in the step 3, in order to ensure that the austenite grains are sufficiently crushed; controlling the single deformation in the rolling process to be more than 15%; controlling the accumulated deformation to be more than 65 percent.
Specifically, in the step 3, in order to achieve the purpose of grain refinement, the water cooling speed is controlled to be 5-15 ℃/s, and the water cooling is controlled to 500-.
Specifically, in the step 4, the quenching process of the steel plate comprises the following steps: and heating the steel plate to the austenitizing temperature T1, preserving heat, and cooling to room temperature by water after preserving heat.
Specifically, in step 4, the austenitizing temperature T1: 860 to 920 ℃; in order to ensure the full austenitizing and quenching effects of the steel plate, the heat preservation time and the quenching roller speed of the steel plate are respectively as follows according to the thickness t (unit is mm):
6-16mm steel plate: the furnace time is (t +30) min; the quenching roller speed is 15-22 m/min;
17-35mm steel plate: the furnace time is (t +40) min; the quenching roller speed is 10-14 m/min;
36-50mm steel plate: the furnace time is (t +50) min; the quenching roller speed is 5-9 m/min;
51-80mm steel plate: the furnace time is (t +60) min; the quenching roller speed is 1-4 m/min.
Specifically, in the step 4, the quenching water temperature is lower than 25 ℃.
Specifically, in the step 4, the tempering process of the steel plate comprises the following steps: the tempering temperature is 630-: (6-7) x t, and the unit of tempering heat preservation time is min; and cooling the tempered steel plate to room temperature by water.
Specifically, through the process, the microstructure of the tempered steel plate is an ultra-low carbon tempered martensite + multi-element nano composite precipitated phase. Specifically, the granularity of the multi-element nano composite precipitated phase is less than 20 nm. The steel plate has yield strength Rp0.2 ≥ 690MPa (e.g. 710-2The fiber rate of impact fracture FA% at minus 40 ℃ is more than or equal to 150J, and the non-uniformity rate of the performance of a single steel plate
Wherein:
in the formula: a represents the rate of performance nonuniformity,%; SD represents the standard deviation of the statistical samples, performance units; si represents a performance unit;
representing the average value of statistical performance and a performance unit; n represents the number of statistical samples, dimensionless.
Compared with the prior art, the invention ensures the easy weldability of the steel plate while ensuring the excellent mechanical property of the steel plate by accurately controlling the mass percentages of elements such as C, Cr, Ni, Mn, Cu and the like in the steel and adopting the design of ultralow carbon and low carbon equivalent.
The invention ensures that the steel structure is ultra-low carbon tempered martensite and multi-element nano composite precipitated phase by adopting a special quenching and tempering heat treatment technology, and the granularity of the multi-element nano composite precipitated phase is less than 20nm, thereby ensuring the obdurability of the steel. Ensuring that the yield strength Rp0.2 is more than or equal to 690MPa (e.g. 710-2The impact fracture fiber rate FA% at-40 ℃ is more than or equal to 150J.
The invention adopts the wide and thick plate rolling mill to ensure the super-wide and super-long size of the steel plate, is applied to the construction of large ocean engineering equipment, can effectively reduce welding seams and welding preheating, thereby greatly reducing the construction cost of the equipment and shortening the construction period.
The embodiment of the invention adopts converter smelting preparation. The chemical compositions of the steels of examples 1-4 are shown in Table 1, the properties of examples 1-4 are shown in Table 2, and the results of the oblique Y-groove weld crack test are shown in Table 3.
Example 1:
the embodiment provides a 690MPa grade steel plate for ocean engineering, the thickness of the steel plate is 6mm, and the specific production process comprises the following steps:
step 1: molten steel is smelted according to the component design, the superheat degree of the molten steel is 13 ℃, the casting speed is 0.8m/min, and a billet with the thickness of 230mm and the width of 2250mm is cast, wherein the chemical components of the billet are shown in Table 1;
step 2: heating the steel billet to 1150 ℃, preserving heat for 90min, removing phosphorus from the steel billet after the steel billet is taken out of a furnace by using high-pressure water, transversely widening the steel plate in 4 passes before rough rolling at the initial rolling temperature of 1130 ℃, longitudinally rolling to the end, accumulating the deformation of the rough rolling by 65.2 percent, cooling the steel plate after rolling at the final rolling temperature of 780 ℃, and finally obtaining the steel plate with the thickness of 6 mm.
And step 3: and (3) carrying out quenching and tempering heat treatment on the steel plate, firstly heating the steel plate to 910 ℃, keeping the temperature in a furnace for 36min, then quenching, wherein the roller speed is 22m/min, the water temperature is 20.7 ℃, the tempering system is 670 ℃ multiplied by 40min, and cooling to room temperature after tempering to obtain the finished steel plate.
The size of the 690MPa super-wide and super-long easily-welded steel plate prepared by the embodiment is 6mm multiplied by 3981mm multiplied by 20170mm, and the mechanical properties of the steel plate are shown in Table 2.
Example 2
The embodiment provides a 690MPa grade steel plate for ocean engineering, the thickness of the steel plate is 24mm, and the specific production process steps are as follows:
step 1: molten steel is smelted according to the component design, the superheat degree of the molten steel is 11 ℃, casting is carried out at the throwing speed of 0.9m/min, and a billet with the thickness of 250mm and the width of 2250mm is cast, wherein the chemical components of the billet are shown in Table 1;
step 2: heating a steel billet to 1150 ℃, preserving heat for 95min, removing phosphorus from the steel billet after the steel billet is taken out of a furnace by using high-pressure water, transversely widening the steel plate in 4 passes before rough rolling at the initial rolling temperature of 1132 ℃, longitudinally rolling to the end, accumulating the deformation of the rough rolling by 68 percent, performing final rolling at the temperature of 803 ℃, performing water cooling after rolling, and finally obtaining the steel plate with the specification of 24mm, wherein the final cooling temperature is 562 ℃.
And step 3: and (3) carrying out quenching and tempering heat treatment on the steel plate, firstly heating the steel plate to 900 ℃, keeping the steel plate in a furnace for 64min, then quenching, wherein the roller speed is 12m/min, the water temperature is 21.5 ℃, the tempering system is 663 ℃ multiplied by 150min, and cooling the steel plate to room temperature after tempering to obtain the finished steel plate.
The size of the 690MPa super-wide and super-long easy-to-weld steel plate prepared by the embodiment is 24mm multiplied by 3990mm multiplied by 16400mm, and the mechanical properties of the steel plate are shown in Table 2.
Example 3
The embodiment provides a 690MPa grade steel plate for ocean engineering, the thickness of the steel plate is 40mm, and the specific production process comprises the following steps:
step 1: molten steel is smelted according to the component design, the superheat degree of the molten steel is 15 ℃, casting is carried out, the throwing speed is 0.9m/min, and a billet with the thickness of 250mm and the width of 2250mm is cast, wherein the chemical components of the billet are shown in table 1;
step 2: heating the steel billet to 1160 ℃, preserving heat for 100min, removing phosphorus from the steel billet after the steel billet is taken out of the furnace by using high-pressure water, transversely widening the steel plate in 4 passes before rough rolling at the initial rolling temperature of 1155 ℃, longitudinally rolling to the end, accumulating the deformation of 70% in the rough rolling, cooling the steel plate after rolling at the final rolling temperature of 827 ℃, and finally obtaining the steel plate with the specification of 40mm, wherein the final cooling temperature is 600 ℃.
And step 3: and (2) carrying out quenching and tempering heat treatment on the steel plate, firstly heating the steel plate to 890 ℃, keeping the steel plate in a furnace for 90min, then quenching, wherein the roll speed is 7m/min, the water temperature is 18.1 ℃, the tempering system is 645 ℃ multiplied by 250min, and cooling the steel plate to room temperature after tempering to obtain the finished steel plate.
The size of the 690MPa super-wide and super-long easy-to-weld steel plate prepared by the embodiment is 40mm multiplied by 4010mm multiplied by 16600mm, and the mechanical properties of the steel plate are shown in Table 2.
Example 4
The embodiment provides a 690MPa grade steel plate for ocean engineering, the thickness of the steel plate is 80mm, and the specific production process steps are as follows:
step 1: molten steel is smelted according to the component design, the molten steel is cast at the superheat degree of 14 ℃, the throwing speed is 0.9m/min, and a billet with the thickness of 300mm and the width of 2250mm is cast, and the chemical components of the billet are shown in table 1;
step 2: heating the steel billet to 1160 ℃, preserving heat for 100min, removing phosphorus from the steel billet after the steel billet is taken out of the furnace by using high-pressure water, transversely widening the steel plate in 4 passes before rough rolling at the initial rolling temperature of 1155 ℃, longitudinally rolling to the end, accumulating the deformation of 72 percent during rough rolling, cooling the steel plate after rolling at the final rolling temperature of 860 ℃, and finally obtaining the steel plate with the specification of 80mm, wherein the final cooling temperature is 650 ℃.
And step 3: carrying out quenching and tempering heat treatment on the steel plate, firstly heating the steel plate to 900 ℃, keeping the temperature in a furnace for 140min, then quenching, wherein the roller speed is 2m/min, the water temperature is 16.1 ℃, the tempering system is 635 ℃ multiplied by 550min, and cooling to room temperature after tempering to obtain the finished steel plate.
The size of the 690MPa super-wide and super-long easy-to-weld steel plate prepared by the embodiment is 80mm multiplied by 3910mm multiplied by 16800mm, and the mechanical properties of the steel plate are shown in Table 2.
The weldability of the industrial steel sheets of examples and comparative examples was evaluated according to GB/T4675.1 oblique Y-groove weld crack test method for weldability test, the test temperature was 0 ℃, the test specimens and grooves were machined according to the standard requirements, the test specimens were dissected according to the standard after natural cooling for 48 hours or more after welding, and the surface crack condition, root crack condition, fracture surface crack condition, and the like of the test specimens were analyzed, and the results are shown in Table 3.
Table 1 examples chemical composition (%)
| C | Si | Mn | S | P | Ni | Cr | Cu | Mo | Als | Ti | V | B | Ceq | |
| Example 1 | 0.025 | 0.03 | 0.75 | 0.001 | 0.006 | 1.76 | 0.54 | 1.21 | 0.4 | 0.028 | 0.01 | 0.04 | 0.000 | 0.544 |
| Example 2 | 0.033 | 0.07 | 0.8 | 0.0013 | 0.008 | 2.04 | 0.51 | 1.3 | 0.46 | 0.04 | 0.03 | 0.03 | 0.000 | 0.589 |
| Example 3 | 0.045 | 0.08 | 0.7 | 0.0011 | 0.0055 | 2.36 | 0.35 | 1.35 | 0.54 | 0.037 | 0.02 | 0.02 | 0.0015 | 0.591 |
| Example 4 | 0.049 | 0.09 | 0.78 | 0.0013 | 0.007 | 2.57 | 0.62 | 1.31 | 0.38 | 0.051 | 0.04 | 0.05 | 0.0027 | 0.648 |
TABLE 2 mechanical properties of the examples
TABLE 3 oblique Y-groove weld crack test results
Through the embodiments, it can be seen that the developed steel plate with the specification of 6-80mm can ensure excellent obdurability matching, the width of the steel plate can exceed 3.9m, the length of the steel plate can exceed 16m, and the steel plate has good cold crack sensitivity under the welding construction condition of 0 ℃, and can realize non-preheating welding.
FIG. 3 is a metallographic structure diagram of a steel sheet according to example 2 of the present invention, and FIG. 4 is a multi-component nanocomposite precipitated phase in the metallographic structure of the steel sheet according to example 2 of the present invention. Therefore, the steel plate with the microstructure of ultra-low carbon tempered martensite and the multi-element nano composite precipitated phase, which has excellent performance, ultra-wide and ultra-long and is easy to weld can be prepared by adopting the components and the method.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. The 690 MPa-grade steel plate for ocean engineering is characterized by comprising the following chemical components in percentage by mass: c: 0.02% -0.05%, Si: 0.05-0.10%, Mn: 0.5% -2.0%, P: not more than 0.008 percent, not more than 0.005 percent of S, Als: 0.01% -0.051%, Ni: 1.0-5.0%, Cr: 0.2% -1.5%, Mo: 0.2% -1.5%, Cu: 0.5% -2.5%, Ti: 0.005% -0.05%, V: 0.005% -0.05%, B: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities.
2. The steel plate for 690MPa grade ocean engineering according to claim 1, wherein the steel plate for 690MPa grade ocean engineering has a carbon equivalent Ceq of 0.65% or less.
3. The steel plate for 690 MPa-grade ocean engineering according to claim 1, wherein the steel plate for 690 MPa-grade ocean engineering comprises the following chemical components in percentage by mass: c: 0.025% -0.049%, Si: 0.03% -0.09%, Mn: 0.7-0.8%, P is less than or equal to 0.008%, S is less than or equal to 0.005%, Als: 0.028% -0.051%, Ni: 1.76% -2.57%, Cr: 0.35-0.62%, Mo: 0.38% -0.54%, Cu: 1.2% -1.35%, Ti: 0.01% -0.04%, V: 0.02% -0.05%, B: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities.
4. The 690MPa grade steel plate for ocean engineering according to any one of claims 1 to 3, wherein the structure of the 690MPa grade steel plate for ocean engineering is an ultra-low carbon tempered martensite + multi-element nano composite precipitated phase.
5. The method for manufacturing the steel plate for 690MPa grade ocean engineering according to claims 1 to 4, comprising:
step 1: smelting molten steel by adopting a converter according to component design, strictly controlling the content of impurity elements in the steel, and continuously casting the steel into a billet;
step 2: heating the steel billet at low temperature and preserving heat for homogenization treatment;
and step 3: removing phosphorus from the steel billet after the steel billet is taken out of the furnace by using high-pressure water, and rolling the steel plate in a wide and thick plate rolling mill, wherein the initial rolling temperature of rough rolling is not lower than 1000 ℃, and the final rolling temperature is 750-860 ℃; after rolling, water cooling is carried out, and air cooling is carried out after the water cooling is carried out to 500-650 ℃;
and 4, step 4: and quenching and high-temperature tempering the rolled steel plate, and then cooling the steel plate to room temperature by water to obtain a finished steel plate.
6. The method for manufacturing the 690MPa grade steel plate for ocean engineering according to claim 5, wherein in the step 1, the superheat degree of casting is controlled to be less than 15 ℃, and the blank drawing speed is controlled to be 0.7-1.1 m/min.
7. The method for manufacturing the 690MPa grade steel plate for ocean engineering according to claim 5, wherein in the step 2, the temperature for low-temperature heating of the billet is 1000-1160 ℃ and the heat preservation time is 1.5-3 h.
8. The method for manufacturing a 690MPa grade steel plate for ocean engineering according to claim 5, wherein in the step 3, the single pass strain amount in the rolling process is controlled to be 15% or more.
9. The method for manufacturing the 690MPa grade steel plate for ocean engineering according to claim 5, wherein in the step 4, the quenching process of the steel plate comprises the following steps: heating the steel plate to an austenitizing temperature T1, preserving heat, and cooling to room temperature by water after preserving heat; wherein the austenitizing temperature T1 is 860-920 ℃, the heat preservation time and the quenching roller speed are respectively as follows according to the thickness T:
6-16mm steel plate: the furnace time is (t +30) min; the quenching roller speed is 15-22 m/min;
17-35mm steel plate: the furnace time is (t +40) min; the quenching roller speed is 10-14 m/min;
36-50mm steel plate: the furnace time is (t +50) min; the quenching roller speed is 5-9 m/min;
51-80mm steel plate: the furnace time is (t +60) min; the quenching roller speed is 1-4 m/min.
10. The method for manufacturing the 690MPa grade steel plate for ocean engineering according to claim 9, wherein in the step 4, the high-temperature tempering process of the steel plate comprises the following steps: the tempering temperature is 630-: (6-7). times.t.
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