CN115369324B - 38MnVS5 rare earth free cutting hot rolled round steel for automobile and preparation method thereof - Google Patents
38MnVS5 rare earth free cutting hot rolled round steel for automobile and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 75
- 239000010959 steel Substances 0.000 title claims abstract description 75
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 32
- 238000005520 cutting process Methods 0.000 title claims abstract description 30
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 14
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 10
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 9
- 239000000126 substance Substances 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 238000005096 rolling process Methods 0.000 claims description 30
- 238000009628 steelmaking Methods 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000005266 casting Methods 0.000 claims description 8
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 4
- 239000011574 phosphorus Substances 0.000 claims description 4
- 239000002893 slag Substances 0.000 claims description 4
- 238000010583 slow cooling Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000011651 chromium Substances 0.000 description 5
- 239000011572 manganese Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 229910000915 Free machining steel Inorganic materials 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000005242 forging Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910019582 Cr V Inorganic materials 0.000 description 1
- 229910000617 Mangalloy Inorganic materials 0.000 description 1
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 1
- 206010057040 Temperature intolerance Diseases 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QFGIVKNKFPCKAW-UHFFFAOYSA-N [Mn].[C] Chemical compound [Mn].[C] QFGIVKNKFPCKAW-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000008543 heat sensitivity Effects 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
-
- 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
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- 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
-
- 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
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- 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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
-
- 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
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses 38MnVS5 rare earth free-cutting hot rolled round steel for an automobile and a preparation method thereof, and the 38MnVS5 rare earth free-cutting hot rolled round steel for the automobile comprises the following chemical components in percentage by mass: c:0.36% -0.40%, mn:1.35% -1.45%, si:0.50% -0.60%, cr:0.12% -0.20%, P is less than or equal to 0.018%, S:0.046% -0.065%, V:0.09-0.11%, RE:0.0010% -0.0020% and the balance of Fe and unavoidable impurities. The 38MnVS5 rare earth free cutting hot rolled round steel for the automobile has excellent plastic toughness and high strength.
Description
Technical Field
The invention belongs to the field of metallurgical materials, and particularly relates to 38MnVS5 rare earth free-cutting hot rolled round steel for an automobile and a preparation method thereof.
Background
The non-quenched and tempered steel is prepared by adding vanadium, titanium and niobium microalloying elements on the basis of medium carbon steel, and dispersing and separating out the alloying elements in C, N by a controlled forging (rolling) process, so that the steel rolled product reaches the quenched and tempered strength level and the mechanical processing performance required by customers in a hot rolling state, a forging state or a normalizing state, thereby omitting quenching and tempering, shortening the production period and saving energy. The non-quenched and tempered steel is widely focused on simplifying the process and saving the cost because the non-quenched and tempered steel does not need subsequent heat treatment after being formed at high temperature, and is gradually applied to various fields.
With the rapid development of the automobile industry, indexes such as automobile safety, stability and energy consumption require automobile parts to be reliable, environment-friendly and weight-reducing; meanwhile, the machining and manufacturing of the automobile parts take a numerical control machine as a center, and higher requirements are put on the cutting performance of materials, so that the free-cutting non-quenched and tempered steel with high strength and toughness becomes the best choice of the automobile parts.
The non-quenched and tempered steel for automobile crankshaft is prepared by adding alloy elements into low and medium carbon manganese steel, and through fine grain strengthening and precipitation strengthening, the strength of the steel reaches the level of quenched and tempered steel, and meanwhile, the steel has certain plasticity and toughness. The traditional free-cutting steel contains Pb element, has excellent processing performance, but the heavy metal element is harmful to the environment, and is gradually eliminated along with the importance of environmental protection; the other is free-cutting steel containing sulfur, the machinability of which improves with an increase in sulfur content, whereas an excessively high sulfur content causes hot shortness during rolling and forging processing. Therefore, a high-strength and high-toughness non-quenched and tempered steel, which is free-cutting steel containing no Pb having excellent machinability, is desired.
Disclosure of Invention
Aiming at the problems existing in the prior art, one aspect of the invention provides 38MnVS5 rare earth free cutting hot rolled round steel for automobiles, which comprises the following chemical components in percentage by mass: c:0.36% -0.40%, mn:1.35% -1.45%, si:0.50% -0.60%, cr:0.12% -0.20%, P is less than or equal to 0.018%, S:0.046% -0.065%, V:0.09-0.11%, RE:0.0010% -0.0020% and the balance of Fe and unavoidable impurities.
The 38MnVS5 rare earth free cutting hot rolled round steel for the automobile comprises the following chemical components in percentage by mass: c:0.37-0.38%, mn:1.40-1.42%, si:0.54-0.55%, V:0.09-0.10%, cr:0.14-0.15%, P is less than or equal to 0.018%, S:0.050-0.057%, RE:0.0013 to 0.0015 percent, and the balance of Fe and unavoidable impurities.
The mechanical properties of the 38MnVS5 rare earth free cutting hot rolled round steel for the automobile meet the following conditions: the yield strength is more than or equal to 570MPa; the tensile strength is more than or equal to 930MPa; the surface shrinkage rate is more than or equal to 45 percent; delay lineThe elongation rate is more than or equal to 16%; room temperature impact work Ak U2 More than or equal to 50J; surface hardness HB240-250.
In another aspect, the invention provides a method for preparing 38MnVS5 rare earth free cutting hot rolled round steel for an automobile, which comprises the following steelmaking process and steel rolling process, wherein the steelmaking process flow comprises: converter-external refining-VD vacuum treatment-continuous casting-slow cooling; the steel rolling process flow comprises the following steps: heating a casting blank, removing phosphorus by high-pressure water, rolling by a cogging machine with the diameter of 850mm, namely rolling by a continuous rolling mill with the diameter of 700mm multiplied by 3 and the diameter of 550mm multiplied by 4;
wherein the following technical parameters are controlled in the steelmaking process flow:
the converter adopts double slag operation, and the final alkalinity is controlled according to 3.0;
the converter end point control target C is more than or equal to 0.09%, and P is less than or equal to 0.020%;
the VD deep vacuum time is more than or equal to 15min, and the soft blowing time is more than or equal to 15min;
the superheat degree is less than or equal to 30 ℃, and the pulling speed of a casting machine is less than or equal to 0.61m/min;
the following technical parameters are controlled in the steel rolling process flow:
the heating temperature is less than or equal to 1220 ℃;
the initial rolling temperature is less than or equal to 1080 ℃;
the finishing temperature is less than or equal to 880 ℃.
Based on the technical scheme, the invention reasonably controls the contents of C, V and Cr elements to further increase the strength and hardness of the product, simultaneously refines grains to increase the plastic toughness of the product, and spheroidizes B, C, D inclusions by adding RE to obtain a pearlite and ferrite metallographic structure to further increase the free-cutting performance of non-quenched and tempered steel, thereby obtaining the 38MnVS5 rare earth free-cutting non-quenched and tempered hot rolled round steel for the automobile with good plastic toughness and higher strength.
Detailed Description
The invention aims to provide 38MnVS5 rare earth free-cutting hot-rolled round steel with excellent comprehensive mechanical properties for automobiles, and also provides a preparation method of the 38MnVS5 rare earth free-cutting hot-rolled round steel for automobiles.
In a first aspect of the invention, a 38MnVS5 rare earth free cutting hot rolled round steel for automobiles is provided, which comprises the following chemical components in percentage by mass: c:0.36% -0.40%, mn:1.35% -1.45%, si:0.50% -0.60%, cr:0.12% -0.20%, P is less than or equal to 0.018%, S:0.046% -0.065%, V:0.09-0.11%, RE:0.0010% -0.0020% and the balance of Fe and unavoidable impurities.
In some embodiments, the mechanical properties of the 38MnVS5 rare earth free cutting hot rolled round steel for automobiles satisfy: the yield strength is more than or equal to 570MPa; the tensile strength is more than or equal to 930MPa; the surface shrinkage rate is more than or equal to 45 percent; the elongation rate is more than or equal to 16%; room temperature impact work Ak U2 More than or equal to 50J; surface hardness HB240-250.
The composition design principle of the 38MnVS5 rare earth free cutting hot rolled round steel for the automobile is as follows:
c: c is the most effective element for improving the strength of the steel, the tensile strength and the yield strength of the steel are improved along with the increase of the content of C, but the elongation and the impact toughness are reduced, the corrosion resistance is also reduced, and the hardening phenomenon also occurs in a welding heat affected zone of the steel, so that welding cold cracks are generated. In order to ensure that the round steel has good comprehensive performance, the content of C element in the steel is designed to be 0.36-0.40%.
Mn: mn is an important toughening element, the cost is low, the strength of the steel is obviously improved along with the increase of the manganese content, the processing performance of the steel is improved, and the ductile-brittle transition temperature is hardly changed. However, too high manganese content can inhibit ferrite transformation, affect the yield strength of steel, and is unfavorable for the control of yield ratio. The Mn element content of the steel is designed to be 1.35-1.45%.
Si: si can improve the strength of steel to a certain extent by increasing Si element, but with further increase of Si mass percent, martensite structure is easy to be generated in steel, so the mass percent of Si is controlled to be 0.50% -0.60%.
V: v and C, O, N have strong binding capacity and form extremely stable compounds with the V, C, O, N, so that grains can be refined, and the heat sensitivity and tempering brittleness of the steel are reduced. Can obviously improve the welding performance of common low alloy steel. The V element content of the steel is designed to be 0.09-0.11%.
Cr: cr can improve the strength, hardness and atmospheric corrosion resistance of steel, and has obvious effect when other alloy elements are added. Chromium can slow down the decomposition rate of austenite, significantly improve the hardenability of steel, and has a secondary hardening effect, but also increases the temper brittleness tendency of steel. However, when the chromium content is too high, toughness of the base material and the heat affected zone is lowered. The Cr element content of the steel is designed to be 0.12% -0.20%.
P, S: p, S are impurity elements in steel. P has a certain effect of improving corrosion resistance, but P is an element easy to segregate, serious segregation is generated on the local part of steel, plasticity and toughness are reduced, and the P is extremely harmful to low-temperature toughness. S element is easy to segregate and concentrate in steel, is an element harmful to corrosion resistance, but has good free-cutting property on steel, so that P is less than or equal to 0.018 percent, and S is as follows: 0.046% -0.060%.
RE: RE is known to be clean and significantly degraded in steel. The cleanliness of steel is continuously improved, and the microalloying effect of rare earth elements is increasingly prominent. The microalloying of rare earth comprises solid solution strengthening of trace rare earth elements, interaction of rare earth elements with other solute elements and compounds, existence state (atoms, inclusions or compounds), size, morphology and distribution of rare earth elements, especially segregation at grain boundaries and influence of rare earth on the surface and matrix structure of steel, and the RE element content in the steel is designed to be 0.0010% -0.0020%.
The invention finally obtains the 38MnVS5 rare earth free cutting hot rolled round steel with excellent comprehensive mechanical properties (especially high plastic toughness) for the automobile through reasonably controlling the content of the elements.
In a second aspect of the invention, a preparation method of 38MnVS5 rare earth free cutting hot rolled round steel for automobiles is provided, which comprises the following processes: the steelmaking process flow comprises the following steps: converter-external refining-VD vacuum treatment-continuous casting-slow cooling; the steel rolling process flow comprises the following steps: heating casting blank, removing phosphorus by high-pressure water, forming a blank machine with the diameter of 850mm, rolling by a continuous rolling mill with the diameter of 700mm multiplied by 3 and the diameter of 550mm multiplied by 4, sawing (sampling), nondestructive testing (ultrasonic flaw detection and eddy current/infrared/magnetic leakage flaw detection), checking, grinding, bundling, warehousing and delivery;
wherein the following technical parameters are controlled in the steelmaking process flow:
the converter adopts double slag operation, and the final alkalinity is controlled according to 3.0;
the converter end point control target C is more than or equal to 0.09%, and P is less than or equal to 0.020%;
the VD deep vacuum time is more than or equal to 15min, and the soft blowing time is more than or equal to 15min;
the superheat degree is less than or equal to 30 ℃, and the pulling speed of a casting machine is less than or equal to 0.61m/min;
the following technical parameters are controlled in the steel rolling process flow:
the heating temperature is less than or equal to 1220 ℃;
the initial rolling temperature is less than or equal to 1080 ℃;
the finishing temperature is less than or equal to 880 ℃.
The following describes the invention in detail by way of specific examples, which are intended to aid in understanding the invention and are not intended to limit the invention.
Examples 1-3: preparation of 38MnVS5 rare earth free cutting hot rolled round steel for automobile
The examples 1-3 aim at producing 38MnVS5 rare earth free cutting hot rolled round steel for automobiles, the chemical compositions and the contents of the 38MnVS5 rare earth free cutting hot rolled round steel for automobiles are shown in the following table 1, and the preparation method specifically comprises the following processes:
the steelmaking process flow comprises the following steps: converter-external refining-VD vacuum treatment-continuous casting-slow cooling; the main technical parameters of the steelmaking process flow are controlled as follows: the converter adopts double slag operation, and the final alkalinity is controlled according to 3.0; the converter end point control target C is more than or equal to 0.09%, and P is less than or equal to 0.020%; the VD deep vacuum time is more than or equal to 15min, and the soft blowing time is more than or equal to 15min; the superheat degree is less than or equal to 30 ℃, the drawing speed of the casting machine is less than or equal to 0.61m/min, and the concrete is shown in the following table 2.
The steel rolling process flow comprises the following steps: heating a casting blank, removing phosphorus by high-pressure water, rolling by a cogging machine with the diameter of 850mm, namely rolling by a continuous rolling mill with the diameter of 700mm multiplied by 3 and the diameter of 550mm multiplied by 4; the main technical parameters controlled in the steel rolling process flow are as follows: the heating temperature is less than or equal to 1220 ℃; the initial rolling temperature is less than or equal to 1080 ℃; the finishing temperature is equal to or lower than 880 ℃, and the concrete is shown in the following table 3.
The mechanical properties of the 38MnVS5 rare earth free cutting hot rolled round steel for automobiles produced in examples 1 to 3 were examined, and the results are shown in Table 4 below.
Table 1: chemical composition and weight percentage content of each example
| Examples | C | Si | Mn | P | S | Cr | V | RE(Ce) |
| 1 | 0.37 | 0.55 | 1.40 | 0.018 | 0.050 | 0.15 | 0.10 | 0.0013 |
| 2 | 0.38 | 0.55 | 1.40 | 0.017 | 0.053 | 0.14 | 0.09 | 0.0014 |
| 3 | 0.37 | 0.54 | 1.42 | 0.018 | 0.057 | 0.15 | 0.10 | 0.0015 |
Table 2: control parameters of steelmaking process of each embodiment
Table 3: example Steel Rolling Process control parameters
| Examples | Heating temperature (. Degree. C.) | Initial rolling temperature (. Degree. C.) | Finishing temperature (. Degree. C.) |
| 1 | 1215 | 1051 | 860 |
| 2 | 1219 | 1050 | 865 |
| 3 | 1220 | 1056 | 870 |
Table 4: mechanical property detection results of the steels prepared in each example
As can be seen from tables 1-4, the invention finally obtains the 38MnVS5 rare earth free cutting hot rolled round steel for the automobile with excellent comprehensive mechanical properties (high plastic toughness and strength) by reasonably controlling the content of chemical components (such as C, V, cr and the like) in the steel and designing reasonable steel-making and steel-rolling processes, and the mechanical properties of the round steel are as follows: the yield strength is more than or equal to 570MPa; the tensile strength is more than or equal to 930MPa; the surface shrinkage rate is more than or equal to 45 percent; the elongation rate is more than or equal to 16%; room temperature impact work Ak U2 More than or equal to 50J; surface hardness HB240-250.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or that equivalents may be substituted for part of the technical features thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (1)
1. The 38MnVS5 rare earth free cutting hot rolled round steel for the automobile comprises the following chemical components in percentage by mass: c:0.37-0.38%, mn:1.40-1.42%, si:0.54-0.55%, V:0.09-0.10%, cr:0.14-0.15%, P is less than or equal to 0.018%, S:0.050-0.057%, RE:0.0013 to 0.0015 percent, and the balance of Fe and unavoidable impurities;
the mechanical properties of the 38MnVS5 rare earth free cutting hot rolled round steel for the automobile meet the following conditions: the yield strength is more than or equal to 570MPa; the tensile strength is more than or equal to 930MPa; the surface shrinkage rate is more than or equal to 45 percent; the elongation rate is more than or equal to 16%; room temperature impact work Ak U2 More than or equal to 50J; surface hardness HB240-250;
the preparation method of the 38MnVS5 rare earth free cutting hot rolled round steel for the automobile comprises the following steelmaking process and steel rolling process, wherein the steelmaking process flow comprises the following steps: converter-external refining-VD vacuum treatment-continuous casting-slow cooling; the steel rolling process flow comprises the following steps: heating a casting blank, removing phosphorus by high-pressure water, rolling by a cogging machine with the diameter of 850mm, namely rolling by a continuous rolling mill with the diameter of 700mm multiplied by 3 and the diameter of 550mm multiplied by 4;
wherein the following technical parameters are controlled in the steelmaking process flow:
the converter adopts double slag operation, and the final alkalinity is controlled according to 3.0;
the converter end point control target C is more than or equal to 0.09%, and P is less than or equal to 0.020%;
the VD deep vacuum time is more than or equal to 15min, and the soft blowing time is more than or equal to 15min;
the superheat degree is less than or equal to 30 ℃, and the pulling speed of a casting machine is less than or equal to 0.61m/min;
the following technical parameters are controlled in the steel rolling process flow:
the heating temperature is less than or equal to 1220 ℃;
the initial rolling temperature is less than or equal to 1080 ℃;
the finishing temperature is less than or equal to 880 ℃.
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