CN114622073B - Method for improving low-temperature impact toughness of boron-containing steel by utilizing sub-temperature quenching - Google Patents
Method for improving low-temperature impact toughness of boron-containing steel by utilizing sub-temperature quenching Download PDFInfo
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- 238000010791 quenching Methods 0.000 title claims abstract description 58
- 230000000171 quenching effect Effects 0.000 title claims abstract description 58
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 55
- 239000010959 steel Substances 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 41
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 title claims abstract description 17
- 229910052796 boron Inorganic materials 0.000 title claims abstract description 17
- 238000005496 tempering Methods 0.000 claims abstract description 30
- 230000008569 process Effects 0.000 claims abstract description 25
- 238000004321 preservation Methods 0.000 claims description 39
- 238000005096 rolling process Methods 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 10
- 239000002893 slag Substances 0.000 claims description 10
- 238000007664 blowing Methods 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- 230000009467 reduction Effects 0.000 claims description 6
- 238000007670 refining Methods 0.000 claims description 6
- 229910001566 austenite Inorganic materials 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- 239000011575 calcium Substances 0.000 claims description 4
- 229910052791 calcium Inorganic materials 0.000 claims description 4
- 238000007872 degassing Methods 0.000 claims description 4
- 238000006477 desulfuration reaction Methods 0.000 claims description 4
- 230000023556 desulfurization Effects 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 238000010079 rubber tapping Methods 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
- 229910052717 sulfur Inorganic materials 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 229910000604 Ferrochrome Inorganic materials 0.000 claims description 2
- 229910001309 Ferromolybdenum Inorganic materials 0.000 claims description 2
- 229910000592 Ferroniobium Inorganic materials 0.000 claims description 2
- 238000003723 Smelting Methods 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 claims description 2
- 238000004364 calculation method Methods 0.000 claims description 2
- 238000005266 casting Methods 0.000 claims description 2
- 238000009749 continuous casting Methods 0.000 claims description 2
- 239000013078 crystal Substances 0.000 claims description 2
- 230000003009 desulfurizing effect Effects 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims description 2
- 238000007667 floating Methods 0.000 claims description 2
- 239000007789 gas Substances 0.000 claims description 2
- 238000000265 homogenisation Methods 0.000 claims description 2
- 239000013072 incoming material Substances 0.000 claims description 2
- ZFGFKQDDQUAJQP-UHFFFAOYSA-N iron niobium Chemical compound [Fe].[Fe].[Nb] ZFGFKQDDQUAJQP-UHFFFAOYSA-N 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims description 2
- 238000003825 pressing Methods 0.000 claims description 2
- 238000001953 recrystallisation Methods 0.000 claims description 2
- 239000006104 solid solution Substances 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- 239000011593 sulfur Substances 0.000 claims description 2
- 230000009466 transformation Effects 0.000 claims description 2
- 238000009849 vacuum degassing Methods 0.000 claims description 2
- 238000009489 vacuum treatment Methods 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 12
- 238000001514 detection method Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Classifications
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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
- C21D8/0205—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
- 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
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- 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
-
- 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
-
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses a method for improving the low-temperature impact toughness of boron-containing steel by utilizing sub-temperature quenching, which mainly solves the technical problems of improving the low-temperature impact toughness and the stability of the boron-containing steel, namely, improving the low-temperature impact toughness of a steel plate by adding a sub-temperature quenching process on the basis of a conventional quenching and tempering process (quenching and high-temperature tempering), and the steel plate produced by adopting the method has excellent low-temperature impact toughness and transverse impact energy at minus 40 ℃): 181J-225J, satisfies the technical requirements of users, and improves the stability of impact performance.
Description
Technical Field
The invention relates to the technical field of metallurgical plate production, in particular to a method for improving low-temperature impact toughness of boron-containing steel by utilizing sub-temperature quenching.
Background
The hydroelectric power generation is used as clean energy, has the characteristics of being renewable, pollution-free, low in operation cost, convenient for carrying out electric power peak regulation and the like, and is beneficial to improving the resource utilization rate. Under the condition of increasingly tense traditional energy sources, the nations worldwide are priced to develop hydropower with priority, and water resources are utilized. Along with the great development of the national large-scale hydroelectric engineering and the increasing of the numerical values of the installed capacity, the water head and the like of a hydropower station, the special hydropower steel for manufacturing the pressure pipeline, the rib plate, the branch pipe, the volute and the like of the large-scale hydropower station is developed towards the high-strength large-thickness direction, the quenching and tempering technology is basically adopted for producing the hydropower steel in each large steel factory for enabling the steel plate to have uniform and stable performance, the hardenability is gradually weakened along with the increase of the thickness of the steel plate, and the steel plate strength is difficult to meet the standard requirement. In order to improve the hardenability of the steel sheet, a trace amount of boron is generally added to improve the hardenability. With the addition of boron, the strength of the steel plate is greatly improved, but the low-temperature impact toughness is obviously reduced, and even the standard requirement is not met. How to improve the low-temperature impact toughness of boron-containing steel is needed to be solved. Sub-temperature quenching, namely quenching the steel plate at the temperature of a two-phase region for proper time, wherein the quenched structure is martensite and a small amount of ferrite.
Disclosure of Invention
The invention aims to provide a method for improving the low-temperature impact toughness of boron-containing steel by utilizing sub-temperature quenching, which is characterized in that the sub-temperature quenching process is added on the basis of the conventional quenching and tempering process (quenching and high-temperature tempering) to improve the low-temperature impact toughness of the steel plate.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention discloses a method for improving low-temperature impact toughness of boron-containing steel by utilizing sub-temperature quenching, which comprises the following steps:
(1) Firstly, desulfurizing the molten iron of the incoming material, removing slag after desulfurization, ensuring that the molten iron after desulfurization has as little slag as possible, and ensuring that the S content after pretreatment is less than or equal to 0.005%;
(2) Smelting in a converter, wherein self-produced low-sulfur scrap steel is adopted, nickel plate alloy is added along with the scrap steel, and bottom blowing gas of the converter adopts a whole-process argon blowing mode, so that the tapping temperature is ensured to be more than or equal to 1620 ℃;
(3) LF external refining and RH vacuum degassing are carried out, LF refining ensures the formation time of white slag, and ferroniobium, ferrochromium and ferromolybdenum are added after the white slag is formed, so as to adjust the white slag to target components; the RH refining stage mainly carries out degassing on molten steel, promotes impurity floating, ensures that the pure degassing time is more than 5 minutes, carries out vacuum treatment for 20 minutes, and then carries out vacuum breaking through re-pressing to carry out calcium treatment, and ensures that the soft blowing time is more than or equal to 10 minutes after the calcium treatment is finished;
(4) Continuous casting of a plate blank, controlling the pulling speed to be 0.80-1.2 m/min, and ensuring the quality of the casting blank by adopting electromagnetic stirring and soft reduction;
(5) Heating the slab, strictly controlling the furnace time, soaking time and tapping temperature of the slab, ensuring austenite homogenization and full solid solution of alloy components, and simultaneously avoiding excessive growth of crystal grains; the furnace time is 240-300 min, the soaking time is 30-60 min, and the furnace discharging temperature is 1200+/-20 ℃;
(6) Primary dephosphorization, rolling and cooling, wherein the slab is subjected to primary dephosphorization after being discharged from the furnace, so that the normal opening of the high-pressure water nozzle is ensured, no blockage is caused, and the dephosphorization pressure is not less than 20MPa; the rough rolling finishes widening in the fewest passes as much as possible, the single-pass relative reduction rate is controlled to be more than 14% for at least 2 passes, the rough rolling ensures the rolling of a recrystallization zone, austenite grains are fully refined, and the final rolling temperature is not less than 1050 ℃; the initial rolling temperature of the finish rolling is not more than 950 ℃, the relative rolling reduction rate of at least 2 passes is more than 14%, rolling in a non-recrystallized region is ensured, tissue and energy preparation is carried out for subsequent phase transformation, and the final rolling temperature of the finish rolling is set to 810-850 ℃; the cooling mode adopts a secondary system self-learning calculation result, and the final cooling temperature is 630-650 ℃;
(7) The conventional tempering heat treatment process comprises the following steps: quenching temperature is 910 ℃ to 920 ℃ and heat preservation time is 20min; tempering temperature is 600-620 ℃, and heat preservation time is 20-40 min;
(8) Adding a sub-temperature quenching heat treatment process, namely adding sub-temperature quenching in conventional quenching, and then carrying out high-temperature tempering: quenching temperature is 910 ℃ to 920 ℃, heat preservation time is 20min, sub-temperature quenching temperature is 865 ℃ to 875 ℃ and heat preservation time is 20min; tempering temperature is 600-620 ℃, and heat preservation time is 20-40 min.
Further, the chemical components of the boron-containing steel are calculated as C: less than or equal to 0.08 percent, si: less than or equal to 0.30 percent, mn: less than or equal to 1.50 percent, P: less than or equal to 0.010%, S less than or equal to 0.005%, alt: 0.020-0.040 percent of Nb less than or equal to 0.060 percent of Ti less than or equal to 0.030 percent of V: less than or equal to 0.050 percent, cr less than or equal to 0.50 percent, mo: less than or equal to 0.50 percent, ni: less than or equal to 0.6 percent, cu less than or equal to 0.5 percent, B less than or equal to 0.0030 percent, and the balance of Fe and unavoidable impurities.
Further, the thickness of the steel plate finished product is 20.0mm, and the heat treatment process comprises the following steps: quenching temperature 910 ℃, heat preservation time 20min, sub-temperature quenching temperature 865 ℃, heat preservation time 20min, tempering temperature 620 ℃ and heat preservation time 20min.
Further, the thickness of the steel plate finished product is 56.0mm, and the heat treatment process comprises the following steps: quenching temperature is 910 ℃, heat preservation time is 20min, sub-temperature quenching temperature is 870 ℃, heat preservation time is 20min, tempering temperature is 620 ℃, and heat preservation time is 30min.
Further, the thickness of the steel plate finished product is 70.0mm, and the heat treatment process comprises the following steps: quenching temperature 920 ℃, heat preservation time 20min, sub-temperature quenching temperature 875 ℃, heat preservation time 20min, tempering temperature 600 ℃ and heat preservation time 30min.
Compared with the prior art, the invention has the beneficial technical effects that:
the steel plate produced by the method has uniform and fine structure, the grain size is about 13 grades, the microstructure is tempered sorbite, a small amount of ferrite and a small amount of residual austenite, the steel plate has excellent low-temperature impact toughness, and all performances meet the technical requirements of users. The steel plate prepared by the method can meet the requirements of hydropower steel with higher strength and larger thickness, and has wide market prospect.
Drawings
The invention is further described with reference to the following description of the drawings.
FIG. 1 is a comparative impact fracture morphology;
FIG. 2 is an impact fracture morphology of example 2.
Detailed Description
The present invention will be described in more detail with reference to specific comparative examples and examples. The examples are merely illustrative of the best mode of the invention and do not limit the scope of the invention in any way.
The invention aims to improve the low-temperature impact toughness of a steel plate by adding a sub-temperature quenching process on the basis of a conventional quenching and tempering process (quenching and high-temperature tempering), so that the chemical compositions of the steel plate of the comparative example and the steel plate of the embodiment are the same, and the chemical compositions are shown in the table 1. Meanwhile, the process route before the tempering heat treatment is basically the same as that of the comparative example, so that the description is omitted, and only the tempering heat treatment process and the sub-temperature quenching process are described below.
Comparative example
The thickness of the steel plate finished product is 38.0mm, and the quenching and tempering heat treatment process parameters are as follows: the quenching temperature is 910 ℃, the heat preservation is 20min, the tempering temperature is 620 ℃, and the heat preservation time is 30min. (1/4 of the plate thickness was sampled for mechanical property detection).
Example 1
The thickness of the steel plate finished product is 20.0mm, and the heat treatment process comprises the following steps: quenching temperature 910 ℃, heat preservation time 20min, sub-temperature quenching temperature 865 ℃, heat preservation time 20min, tempering temperature 620 ℃ and heat preservation time 20min. (the steel plate is sampled in full thickness for mechanical property detection).
Example 2
The thickness of the steel plate finished product is 56.0mm, and the heat treatment process comprises the following steps: quenching temperature is 910 ℃, heat preservation time is 20min, sub-temperature quenching temperature is 870 ℃, heat preservation time is 20min, tempering temperature is 620 ℃, and heat preservation time is 30min. (1/4 of the plate thickness was sampled for mechanical property detection).
Example 3
The thickness of the finished product is 70.0mm, and the heat treatment process comprises the following steps: quenching temperature 920 ℃, heat preservation time 20min, sub-temperature quenching temperature 875 ℃, heat preservation time 20min, tempering temperature 600 ℃ and heat preservation time 30min. (1/4 of the plate thickness was sampled for mechanical property detection).
TABLE 1 chemical composition (wt%) of comparative examples and examples of the present invention
| C | Si | Mn | P | S | Alt | Nb | Ti | V | Cr | Mo | Ni | Cu | B |
| 0.075 | 0.25 | 1.34 | 0.008 | 0.005 | 0.045 | 0.040 | 0.019 | 0.045 | 0.45 | 0.36 | 0.50 | 0.19 | 0.0015 |
The mechanical properties of the steel plates of the comparative example and the example of the present invention were examined, and the examination results are shown in Table 2.
TABLE 2 mechanical Properties of comparative examples and examples of the invention
As can be seen from the data in Table 2, the yield strength, tensile strength, elongation and 180 ℃ cold bending performance indexes of the comparative examples and the examples can meet the technical requirements of users. However, the comparative example has lower transverse low-temperature impact energy at-40 ℃, does not meet the standard requirement, and has poor impact energy numerical stability; the steel plate produced by the method (examples 1-3) has higher transverse low-temperature impact energy at-40 ℃, meets the technical requirements, and has good impact energy numerical stability.
FIGS. 1 and 2 show the morphology of impact fracture of the steel plates of comparative example and example 2, respectively, and it can be seen that the impact fracture of the comparative example is in a cleavage shape, belongs to brittle fracture, and has lower impact energy; the impact fracture of the example 2 is in a ductile nest shape, belongs to ductile fracture and has higher impact energy.
The invention aims to solve the technical problem of improving the low-temperature impact toughness and the stability of boron-containing steel, namely, improving the low-temperature impact toughness of the steel plate by adding a sub-temperature quenching process on the basis of a conventional quenching and tempering process (quenching and high-temperature tempering). The steel plate produced by the invention has excellent low-temperature impact toughness and transverse impact energy at minus 40 ℃): 181J-225J, satisfies the technical requirements of users, and improves the stability of impact performance.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (4)
1. A method for improving the low-temperature impact toughness of boron-containing steel by using sub-temperature quenching, which is characterized by comprising the following steps:
(1) Firstly, desulfurizing the molten iron of the incoming material, removing slag after desulfurization, ensuring that the molten iron after desulfurization has as little slag as possible, and ensuring that the S content after pretreatment is less than or equal to 0.005%;
(2) Smelting in a converter, wherein self-produced low-sulfur scrap steel is adopted, nickel plate alloy is added along with the scrap steel, and bottom blowing gas of the converter adopts a whole-process argon blowing mode, so that the tapping temperature is ensured to be more than or equal to 1620 ℃;
(3) LF external refining and RH vacuum degassing are carried out, LF refining ensures the formation time of white slag, and ferroniobium, ferrochromium and ferromolybdenum are added after the white slag is formed, so as to adjust the white slag to target components; the RH refining stage mainly carries out degassing on molten steel, promotes impurity floating, ensures that the pure degassing time is more than 5 minutes, carries out vacuum treatment for 20 minutes, and then carries out vacuum breaking through re-pressing to carry out calcium treatment, and ensures that the soft blowing time is more than or equal to 10 minutes after the calcium treatment is finished;
(4) Continuous casting of a plate blank, wherein the pulling speed is controlled to be 0.80-1.2 m/min, and the quality of the casting blank is ensured by adopting electromagnetic stirring and soft reduction;
(5) Heating the slab, strictly controlling the furnace time, soaking time and tapping temperature of the slab, ensuring austenite homogenization and full solid solution of alloy components, and simultaneously avoiding excessive growth of crystal grains; the furnace time is 240-300 min, the soaking time is 30-60 min, and the furnace discharging temperature is 1200+/-20 ℃;
(6) Primary dephosphorization, rolling and cooling, wherein the slab is subjected to primary dephosphorization after being discharged from the furnace, so that the normal opening of the high-pressure water nozzle is ensured, no blockage is caused, and the dephosphorization pressure is not less than 20MPa; the rough rolling finishes widening in the fewest passes as much as possible, the single-pass relative reduction rate is controlled to be more than 14% for at least 2 passes, the rough rolling ensures the rolling of a recrystallization zone, austenite grains are fully refined, and the final rolling temperature is not less than 1050 ℃; the initial rolling temperature of the finish rolling is not more than 950 ℃, the relative rolling reduction rate of at least 2 passes is more than 14%, rolling in a non-recrystallized zone is ensured, tissue and energy preparation is carried out for subsequent phase transformation, and the final rolling temperature of the finish rolling is set to 810-850 ℃; the cooling mode adopts a secondary system self-learning calculation result, and the final cooling temperature is 630-650 ℃;
(7) The conventional tempering heat treatment process comprises the following steps: quenching temperature is 910-920 ℃, and heat preservation time is 20min; tempering temperature is 600-620 ℃, and heat preservation time is 20-40 min;
(8) Adding a sub-temperature quenching heat treatment process, namely adding sub-temperature quenching in conventional quenching, and then carrying out high-temperature tempering: quenching temperature is 910 ℃ to 920 ℃, heat preservation time is 20min, sub-temperature quenching temperature is 865 ℃ to 875 ℃ and heat preservation time is 20min; tempering temperature is 600-620 ℃, and heat preservation time is 20-40 min;
the boron-containing steel comprises the following chemical components in percentage by mass: less than or equal to 0.08 percent, si: less than or equal to 0.30 percent, mn: less than or equal to 1.50 percent, P: less than or equal to 0.010%, S less than or equal to 0.005%, alt: 0.020-0.040%, nb less than or equal to 0.060%, ti less than or equal to 0.030%, V: less than or equal to 0.050 percent, cr less than or equal to 0.50 percent, mo: less than or equal to 0.50 percent, ni: less than or equal to 0.6 percent, cu less than or equal to 0.5 percent, B less than or equal to 0.0030 percent, and the balance of Fe and unavoidable impurities.
2. The method for improving the low-temperature impact toughness of boron-containing steel by using sub-temperature quenching according to claim 1, wherein the thickness of a finished steel plate is 20.0mm, and the heat treatment process comprises the following steps: quenching temperature 910 ℃, heat preservation time 20min, sub-temperature quenching temperature 865 ℃, heat preservation time 20min, tempering temperature 620 ℃ and heat preservation time 20min.
3. The method for improving the low-temperature impact toughness of boron-containing steel by using sub-temperature quenching according to claim 1, wherein the thickness of a finished steel plate is 56.0mm, and the heat treatment process comprises the following steps: quenching temperature is 910 ℃, heat preservation time is 20min, sub-temperature quenching temperature is 870 ℃, heat preservation time is 20min, tempering temperature is 620 ℃, and heat preservation time is 30min.
4. The method for improving the low-temperature impact toughness of boron-containing steel by using sub-temperature quenching according to claim 1, wherein the thickness of a finished steel plate is 70.0mm, and the heat treatment process comprises the following steps: quenching temperature 920 ℃, heat preservation time 20min, sub-temperature quenching temperature 875 ℃, heat preservation time 20min, tempering temperature 600 ℃ and heat preservation time 30min.
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