CN116640997A - Economical 690 Pa-grade quenched and tempered high-strength steel plate without niobium and manufacturing method - Google Patents
Economical 690 Pa-grade quenched and tempered high-strength steel plate without niobium and manufacturing method Download PDFInfo
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- CN116640997A CN116640997A CN202310706508.2A CN202310706508A CN116640997A CN 116640997 A CN116640997 A CN 116640997A CN 202310706508 A CN202310706508 A CN 202310706508A CN 116640997 A CN116640997 A CN 116640997A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 65
- 239000010959 steel Substances 0.000 title claims abstract description 65
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 26
- 229910052758 niobium Inorganic materials 0.000 title claims abstract description 12
- 239000010955 niobium Substances 0.000 title claims abstract description 12
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 title claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 50
- 238000005096 rolling process Methods 0.000 claims abstract description 46
- 238000005496 tempering Methods 0.000 claims abstract description 33
- 238000003723 Smelting Methods 0.000 claims abstract description 24
- 238000010438 heat treatment Methods 0.000 claims abstract description 19
- 239000012535 impurity Substances 0.000 claims abstract description 11
- 238000009749 continuous casting Methods 0.000 claims abstract description 7
- 239000000126 substance Substances 0.000 claims abstract description 4
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 4
- 238000005266 casting Methods 0.000 claims description 28
- 238000001816 cooling Methods 0.000 claims description 28
- 238000010791 quenching Methods 0.000 claims description 21
- 230000000171 quenching effect Effects 0.000 claims description 21
- 238000003756 stirring Methods 0.000 claims description 13
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 10
- 229910045601 alloy Inorganic materials 0.000 claims description 10
- 239000000956 alloy Substances 0.000 claims description 10
- 229910052791 calcium Inorganic materials 0.000 claims description 10
- 239000011575 calcium Substances 0.000 claims description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 9
- 229910000746 Structural steel Inorganic materials 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 4
- 238000005516 engineering process Methods 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 238000007670 refining Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000009489 vacuum treatment Methods 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims 1
- 238000006477 desulfuration reaction Methods 0.000 claims 1
- 230000023556 desulfurization Effects 0.000 claims 1
- 229910001563 bainite Inorganic materials 0.000 abstract description 12
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 238000003466 welding Methods 0.000 description 9
- 239000000463 material Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- RMLPZKRPSQVRAB-UHFFFAOYSA-N tris(3-methylphenyl) phosphate Chemical compound CC1=CC=CC(OP(=O)(OC=2C=C(C)C=CC=2)OC=2C=C(C)C=CC=2)=C1 RMLPZKRPSQVRAB-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
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- C—CHEMISTRY; METALLURGY
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
-
- C—CHEMISTRY; METALLURGY
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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Abstract
The invention discloses an economic type 690 Pa-grade quenched and tempered high-strength steel plate without niobium and a manufacturing method thereof. Belonging to the technical field of steel production; the chemical components are as follows: C. si, mn, P, S, ti, V, cr, mo, alt and B, the balance being Fe and impurities; the method comprises the following steps: smelting process, continuous casting process, heating process, rolling and tempering process, etc.; the invention provides an economical 690MPa high-strength steel plate with excellent comprehensive performance and a production method thereof; the lath bainite and granular bainite are obtained, and the microstructure is uniform and fine; the lath bainite and granular bainite structure is beneficial to maintaining strength and excellent plasticity and toughness.
Description
Technical Field
The invention relates to the technical field of steel production, in particular to an economic 690 Pa-grade quenched and tempered high-strength steel plate without niobium and a manufacturing method thereof.
Background
In the prior art, the 690 Pa-grade quenched and tempered high-strength weldable steel plate under American standard is mainly used in places requiring high tensile strength and high yield, engineering mechanical suspension arms, engineering car lifting gears and the like; general trend of high-strength steel: high strength, light weight and easy welding.
The 690 Pa-grade quenched and tempered high-strength steel plate has more application advantages, and the application of the high-strength steel can reduce the material cost, the transportation cost and the manufacturing cost; the consumption of welding materials can be saved, and the post-welding stress can be reduced during welding; reducing the preheating temperature of welding, reducing the heat treatment requirement after welding, and the like.
With the continuous progress of steel materials, welding materials manufacturing and welding process technologies, the strength level of structural steel is continuously improved, the steel grade with the strength level of more than 1000MPa is frequently fresh, and the total demand of high-strength steel is increased year by year. Marine cranes, marine tanks, jack-up platform legs, coal mine hydraulic supports and the like are used with Q690 high-strength steel in many cases; in automobiles, containers, engineering machinery pump trucks, cranes, etc., so-called ultra-high strength steels Q800, Q890, Q960, even higher strength Q1100, Q1300, Q1600, etc. are used. For the field of high-strength steel, 690 MPa-level high-strength steel is a steel grade for a large number of applications; although high strength steels such as Q800 and Q960 have been tried, the materials are limited by the welding and matching, and the higher strength steels have been rarely used successfully.
Therefore, it is necessary to develop an economical 690 Pa-grade quenched and tempered high-strength steel plate without niobium, and a complete set of steelmaking, rolling cooling and quenching and tempering processes are formed, so that the production cost is reduced, the process is easy to operate, and the product performance is stable.
Disclosure of Invention
The invention aims to: the invention aims to provide an economical 690MPa high-strength steel plate with excellent comprehensive performance and a production method thereof; the lath bainite and granular bainite obtained by the method have uniform and fine tissues; in addition, the lath bainite and granular bainite have structures which are beneficial to maintaining strength and excellent toughness.
The technical scheme is as follows: the economic type non-niobium 690 Pa-grade quenched and tempered high-strength steel plate comprises the following chemical components in percentage by mass: c:0.15 to 0.18 percent of Si:0.20 to 0.35 percent of Mn: 0.7-1.00%, P: less than or equal to 0.013 percent, S: less than or equal to 0.003 percent, ti:0.010 to 0.020%, V:0.030 to 0.050 percent, cr:0.45 to 0.55 percent of Mo:0.15 to 0.25 percent, alt:0.020 to 0.040 percent, B: 0.0005-0.005%, and the balance of Fe and impurities.
Furthermore, the smelting process of the calcium treatment is combined with the casting process of dynamic soft reduction and electromagnetic stirring to improve the internal quality of the casting blank while ensuring the content of alloy components and impurity elements through smelting; adopting a precise rolling and precise cooling control process in a rolling control and cooling control stage;
firstly, smelting ensures the content of alloy components and impurity elements, and the smelting process of calcium treatment ensures the control of inclusions in the steel plate;
secondly, the internal quality of the casting blank is improved by adopting a casting process of dynamic soft reduction and electromagnetic stirring, and the level of central macrosegregation and microsegregation of the casting blank is effectively reduced;
the accurate rolling control process and tempering process are controlled to be smaller in cooling speed by adopting a weak cooling mode in the cooling control stage, so that more toughness tissues are obtained. The toughness of the steel plate is improved through inclusion control and structure control;
finally, quenching and subsequent high temperature tempering, i.e. tempering, are employed. The steel plate after quenching and tempering has better comprehensive mechanical properties of strength, plasticity and toughness, and is widely applied to various important structural members manufactured by medium carbon structural steel, such as engine crankshafts, connecting rod machine tool spindles, gears and the like.
Furthermore, the preparation method of the economic type non-niobium 690 Pa-grade quenched and tempered high-strength steel plate comprises the following specific preparation steps:
step (1), smelting process;
step (2), a continuous casting process;
step (3), heating process;
step (4), a rolling process;
and (5) tempering.
Further, in the step (1), the smelting process specifically includes: the molten iron is pretreated, desulfurized in advance, blown in a converter, alloy components are regulated through LF refining, the purity of molten steel is improved through RH vacuum treatment, and a smelting process of calcium treatment is implemented after soft stirring is finished, so that the molten steel with high purity and qualified components is ensured to be obtained.
Further, in the step (2), the continuous casting process specifically includes: the excellent internal quality of the casting blank is realized by adopting dynamic soft reduction and electromagnetic stirring technology.
Further, in the step (3), the heating process specifically includes: the casting blank with the thickness of 260mm enters a heating furnace, the heating temperature of the casting blank is 1160-1200 ℃, the furnace time is 230-350 min, and the discharging temperature is 1160-1200 ℃.
Further, in the step (4), the rolling process specifically includes: adopting two-stage rolling, wherein the rough rolling temperature is 950-1150 ℃, the finish rolling initial rolling temperature is 850-900 ℃, and the finish rolling final rolling temperature is 800-850 ℃; and then cooling by laminar flow, wherein the redback temperature is 640-700 ℃. The cooling rate is 1-20 ℃/s. The thickness of the finished steel plate is 6-50mm.
Further, in the step (5), the tempering process is tempering heat treatment, specifically: quenching temperature is 900-950 ℃ and quenching time is 15-100 min; the tempering temperature is 500-650 ℃ and the tempering time is 20-200 min.
According to the invention, an economic type non-niobium 690 Pa-grade quenched and tempered high-strength steel plate is developed to form a complete set of steelmaking, rolling cooling and quenching and tempering processes, so that the production cost is reduced, the process is easy to operate, and the product performance is stable.
The beneficial effects are that: compared with the prior art, the invention has the characteristics that: 1. the smelting process of smelting to ensure the content of alloy components and impurity elements and calcium treatment is adopted, and the casting process of dynamic soft reduction and electromagnetic stirring is combined to improve the internal quality of a casting blank and ensure the plasticity and toughness of a steel plate; 2. the manufacturing method of the invention has simple process and lower cost, adopts a blank with the thickness of 260mm, and produces the 690 Pa-grade quenched and tempered high-strength steel plate which has economical niobium-free high strength and toughness and is easy to weld through a controlled rolling and controlled cooling and quenching and tempering process; 3. the manufacturing method of the invention has stable performance: the yield strength is between 700 and 800MPa, the elongation A50 is more than or equal to 17 percent, and the impact energy at minus 20 ℃ is more than or equal to 120J.
Drawings
FIG. 1 is a typical structure morphology diagram of a weather-resistant bridge steel plate with the thickness of 20mm obtained after quenching and tempering in the embodiment 1 of the invention under a metallographic microscope;
FIG. 2 is a typical structure morphology diagram of a weather-resistant bridge steel plate with the thickness of 50mm obtained after the tempering treatment in the embodiment 2 of the invention under a metallographic microscope.
Detailed Description
The invention is further illustrated below with reference to examples.
As shown in the figure, the smelting process of the calcium treatment is combined with the casting process of dynamic soft reduction and electromagnetic stirring to improve the internal quality of a casting blank while ensuring the content of alloy components and impurity elements through smelting; adopting a precise rolling and precise cooling control process in a rolling control and cooling control stage;
firstly, smelting ensures the content of alloy components and impurity elements, and the smelting process of calcium treatment ensures the control of inclusions in the steel plate;
secondly, the internal quality of the casting blank is improved by adopting a casting process of dynamic soft reduction and electromagnetic stirring, and the level of central macrosegregation and microsegregation of the casting blank is effectively reduced;
the accurate rolling control process and tempering process are controlled to be smaller in cooling speed by adopting a weak cooling mode in the cooling control stage, so that more toughness tissues are obtained; the toughness of the steel plate is improved through inclusion control and structure control.
Finally, quenching and subsequent high-temperature tempering, namely quenching and tempering treatment are adopted; the steel plate after quenching and tempering has better comprehensive mechanical properties of strength, plasticity and toughness, and is widely applied to various important structural members manufactured by medium carbon structural steel, such as engine crankshafts, connecting rod machine tool spindles, gears and the like.
Specifically, the invention comprises a smelting process, a continuous casting process, a heating process, a rolling process, a quenching and tempering process and the like.
The specific parameters in the process are controlled as follows:
(1) Smelting: the molten iron is pretreated, desulfurized in advance, blown in a converter, alloy components are regulated through LF refining, the purity of molten steel is improved through RH vacuum treatment, and a smelting process of calcium treatment is implemented after soft stirring is finished, so that molten steel with high purity and qualified components is ensured to be obtained;
(2) Continuous casting: adopting dynamic soft reduction and electromagnetic stirring technology to realize excellent internal quality of casting blank;
(3) And (3) heating: feeding a casting blank with the thickness of 260mm into a heating furnace, wherein the heating temperature of the casting blank is 1160-1200 ℃, the furnace time is 230-350 min, and the discharging temperature is 1160-1200 ℃;
(4) Rolling: adopting two-stage rolling, wherein the rough rolling temperature is 950-1150 ℃, the finish rolling initial rolling temperature is 850-900 ℃, and the finish rolling final rolling temperature is 800-850 ℃; and then cooling by laminar flow, wherein the redback temperature is 640-700 ℃. The cooling rate is 1-20 ℃/s. The thickness of the finished steel plate is 6-50mm;
(5) And (3) heat treatment: quenching temperature is 900-950 ℃ and quenching time is 15-100 min; the tempering temperature is 500-650 ℃ and the tempering time is 20-200 min.
The steel comprises the following components in percentage by weight: 0.15 to 0.18 percent of Si:0.20 to 0.35 percent of Mn: 0.7-1.00%, P: less than or equal to 0.013 percent, S: less than or equal to 0.003 percent, ti:0.010 to 0.020%, V:0.030 to 0.050 percent, cr:0.45 to 0.55 percent of Mo:0.15 to 0.25 percent, alt:0.020 to 0.040 percent, B: 0.0005-0.005%, and the balance of Fe and impurities.
Example 1
An economical 690 Pa-grade quenched and tempered high-strength steel plate without niobium and a production method thereof, wherein the components are shown in a weight percentage ratio in table 1.
The economical 690 Pa-grade quenched and tempered high-strength steel plate without niobium and the production method thereof specifically require the following steps:
and (3) a rolling and cooling control process: adopting a rolling control and cooling control process (TMCP) to roll in two stages; feeding a casting blank with the thickness of 260mm into a heating furnace, wherein the heating temperature of the casting blank is 1160-1200 ℃, the furnace time is 230-350 min, and the discharging temperature is 1160-1200 ℃; the rough rolling temperature is 950-1150 ℃, the finish rolling initial rolling temperature is 850-900 ℃, and the finish rolling final rolling temperature is 800-850 ℃; and then cooling by laminar flow, wherein the redback temperature is 640-700 ℃. The cooling rate is 1-20 ℃/s. The thickness of the finished steel plate is 6-50mm.
And (3) tempering: quenching temperature is 900-950 ℃ and quenching time is 15-100 min; the tempering temperature is 500-650 ℃ and the tempering time is 20-200 min.
FIGS. 1 and 2 are typical structure morphology diagrams of 690 Pa-grade quenched and tempered high-strength steel plates obtained after quenching and tempering in an embodiment under a metallographic microscope; the tissue is uniform and fine; by carefully observing FIGS. 1 and 2, it can be seen that the upper lath bainite plus granular bainite in the structure has a uniform and fine structure. The lath bainite and granular bainite structure is beneficial to maintaining strength and excellent plasticity and toughness.
The properties of the finished steel sheet are shown in tables 2-3 below.
TABLE 1 chemical composition (wt%) of the examples of the present invention
| Examples | C | Si | Mn | P | S | Alt | V | Ti | Cr | Mo | B |
| Example 1 | 0.16 | 0.28 | 0.89 | 0.013 | 0.004 | 0.034 | 0.040 | 0.013 | 0.51 | 0.22 | 0.0014 |
| Example 2 | 0.17 | 0.26 | 0.95 | 0.012 | 0.003 | 0.032 | 0.035 | 0.015 | 0.46 | 0.18 | 0.0015 |
TABLE 2 tensile Properties
TABLE 3 series temperature impact Properties
It can be seen that the mechanical properties of the examples 1 and 2 meet the requirements of 690 MPa-grade quenched and tempered high-strength steel plates; the properties of the specific steel sheet reached the following levels: the yield strength is between 700 and 800MPa, the elongation A50 is more than or equal to 17 percent, and the impact energy at minus 20 ℃ is more than or equal to 120J.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the invention without departing from the principles thereof are intended to be within the scope of the invention as set forth in the following claims.
Claims (10)
1. An economic 690 Pa-grade quenched and tempered high-strength steel plate without niobium is characterized by comprising the following chemical components in percentage by mass: c:0.15 to 0.18 percent of Si:0.20 to 0.35 percent of Mn: 0.7-1.00%, P: less than or equal to 0.013 percent, S: less than or equal to 0.003 percent, ti:0.010 to 0.020%, V:0.030 to 0.050 percent, cr:0.45 to 0.55 percent of Mo:0.15 to 0.25 percent, alt:0.020 to 0.040 percent, B: 0.0005-0.005%, and the balance of Fe and impurities.
2. The method for manufacturing an economical, non-niobium 690 Pa-grade quenched and tempered high-strength steel plate according to claim 1, wherein the smelting process of ensuring the content of alloy components and impurity elements through smelting and simultaneously carrying out calcium treatment is combined with the casting process of dynamic soft reduction and electromagnetic stirring to improve the internal quality of a casting blank; adopting a precise rolling and precise cooling control process in a rolling control and cooling control stage;
firstly, smelting ensures the content of alloy components and impurity elements, and the smelting process of calcium treatment ensures the control of inclusions in the steel plate;
secondly, a casting process of dynamic soft reduction and electromagnetic stirring is adopted, so that the internal quality of the casting blank is improved, and the level of central macrosegregation and microsegregation of the casting blank is reduced;
the accurate rolling control process and tempering process are controlled to be low in cooling speed by adopting a weak cooling mode in the cooling control stage, so that a tough structure is obtained; the toughness of the steel plate is improved through inclusion control and structure control;
finally, quenching and subsequent high-temperature tempering, namely quenching and tempering treatment are adopted; the method is applied to various important structural members manufactured by medium carbon structural steel.
3. The method for manufacturing an economical, niobium-free 690 Pa-grade quenched and tempered high-strength steel plate according to claim 2, wherein the specific manufacturing steps are as follows:
step (1), smelting process;
step (2), a continuous casting process;
step (3), heating process;
step (4), a rolling process;
and (5) tempering.
4. The method for producing an economical, niobium-free 690 Pa-grade tempered high-strength steel plate as claimed in claim 3, wherein,
in the step (1), the smelting process specifically includes: the molten iron pretreatment is used for pre-desulfurization, converter blowing is carried out, alloy components are regulated through LF refining, RH vacuum treatment is adopted to improve the purity of molten steel, and a smelting process of calcium treatment is carried out after soft stirring is finished, so that molten steel with high purity and qualified components is obtained.
5. The method for producing an economical, niobium-free 690 Pa-grade tempered high-strength steel plate as claimed in claim 3, wherein,
in the step (2), the continuous casting process specifically includes: and the internal quality of the casting blank is realized by adopting dynamic soft reduction and electromagnetic stirring technology.
6. The method for producing an economical, niobium-free 690 Pa-grade tempered high-strength steel plate as claimed in claim 3, wherein,
in the step (3), the heating process specifically includes: and (3) feeding a casting blank with the thickness of 260mm into a heating furnace, wherein the heating temperature of the casting blank is 1160-1200 ℃, the furnace time is 230-350 min, and the furnace discharging temperature is 1160-1200 ℃.
7. The method for producing an economical, niobium-free 690 Pa-grade tempered high-strength steel plate as claimed in claim 3, wherein,
in the step (4), the rolling process specifically includes: two-stage rolling is employed, including rough rolling and finish rolling.
8. The method for producing an economical, niobium-free 690 Pa-grade tempered high-strength steel plate as claimed in claim 7, wherein,
the rough rolling temperature is 950-1150 ℃;
the initial rolling temperature of the finish rolling is 850-900 ℃, and the final rolling temperature of the finish rolling is 800-850 ℃; then laminar cooling is carried out, and the redback temperature is 640-700 ℃; the cooling rate is 1-20 ℃/s.
9. The method for producing an economical, niobium-free 690 Pa-grade tempered high-strength steel plate as claimed in claim 8, wherein,
the thickness of the finished steel plate is 6-50mm.
10. The method for producing an economical, niobium-free 690 Pa-grade tempered high-strength steel plate as claimed in claim 3, wherein,
in the step (5), the tempering process is heat treatment, specifically: quenching temperature is 900-950 ℃ and quenching time is 15-100 min; the tempering temperature is 500-650 ℃ and the tempering time is 20-200 min.
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