CN112410670B - Bainite/martensite type non-quenched and tempered steel - Google Patents
Bainite/martensite type non-quenched and tempered steel Download PDFInfo
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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
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R19/00—Wheel guards; Radiator guards, e.g. grilles; Obstruction removers; Fittings damping bouncing force in collisions
- B60R19/02—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects
- B60R19/03—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects characterised by material, e.g. composite
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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
- C22C38/06—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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- 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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- 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
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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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
- C21D2211/002—Bainite
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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
- C21D2211/008—Martensite
Abstract
The invention provides bainite/martensite non-quenched and tempered steel. The composition comprises the following components in percentage by mass: 0.20 to 0.25 percent of C; 0.40 to 0.50 percent of Si; 1.90 to 2.10 percent of Mn1; p is less than or equal to 0.0080 percent; s0.035% -0.055%; 0.50 to 0.60 percent of Cr; v0.10% -0.20%; 0.03-0.05% of Ti; 0.015 to 0.035 percent of Al; 0.006 percent to 0.008 percent of N; less than or equal to 0.001 percent of O, and the balance of iron and inevitable impurities. The tensile strength of the novel bainite/martensite type non-quenched and tempered steel provided by the invention can reach 1300MPa, the yield strength can reach 900MPa, and the reduction of area can reach 50%, compared with the existing ferrite and pearlite type non-quenched and tempered steel, the novel bainite/martensite type non-quenched and tempered steel has the advantages of high strength, good toughness and the like, and can be used for replacing the quenched and tempered steel to produce safety parts such as automobile bumpers and the like; has the advantages of energy conservation, environmental protection, low cost and the like.
Description
Technical Field
The invention relates to the technical field of alloy steel, in particular to bainite/martensite non-quenched and tempered steel.
Background
Compared with the conventional quenched and tempered steel production process, the processes of quenching, high-temperature tempering, straightening and the like are omitted in the production process of non-quenched and tempered steel, the production process flow is simplified, the energy is saved, and the manufacturing cost is reduced, so that the non-quenched and tempered steel is more and more applied to the mechanical manufacturing industry of automobiles and the like. Non-quenched and tempered steels can be classified into ferrite + pearlite type non-quenched and tempered steels, bainite type non-quenched and tempered steels, and martensite type non-quenched and tempered steels according to the microstructure form. At present, ferrite + pearlite type non-quenched and tempered steel which is most researched and widely applied, such as C70S6, 38MnVS, 46MnVS, C38N2 and the like, has successfully replaced 42CrMo and 40Cr and is used for producing automobile parts such as automobile connecting rods, crankshafts, half shafts, steering knuckles and the like. Ferrite and pearlite type non-quenched and tempered steel is generally applied to the grade below 1000MPa, and has lower strength and poorer plasticity and toughness. Therefore, non-heat-treated steels of bainite type and martensite type, which have higher strength and better toughness, have been developed and applied. Due to the structural characteristics of the martensite type non-quenched and tempered steel, the martensite type non-quenched and tempered steel still needs tempering treatment when being applied, and the advantages are not obvious compared with quenched and tempered steel. The bainite type non-quenched and tempered steel or the bainite/martensite type non-quenched and tempered steel has the characteristics of excellent performance, simple production process and the like, and has greater development potential.
At present, the majority of bainite non-quenched and tempered steels applied are 25MnCrSiVB6, 12Mn2VBS, 25Mn2CrV (FAS2225) and the like, and generally low-carbon steel is added with elements for enlarging bainite transformation area and refining crystal grains, and the cooling speed is controlled to obtain low-carbon bainite structure so as to realize matrix strengthening. The main components and mechanical properties of bainite non-quenched and tempered steel commonly used in the prior art are shown in table 1.
TABLE 1 mechanical properties of common bainite type non-quenched and tempered steels
In recent years, development work of bainite type non-heat treated steel has been advanced. For example, the prior art discloses a low-carbon bainite type Nb-V composite microalloyed non-quenched and tempered steel and a preparation method thereof, the method provides that the strength of the bainite steel is improved by Nb-V composite, when the forging ratio is 7, the tensile strength can reach 1000MPa, but the requirement of the non-quenched steel on the increasingly improved strength level is still difficult to meet.
Disclosure of Invention
Embodiments of the present invention provide a bainite/martensite type non-heat-treated steel to overcome the problems of the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme.
A bainite/martensite type non-quenched and tempered steel comprises the following components in percentage by mass: 0.20 to 0.25 percent of C; 0.40 to 0.50 percent of Si; 1.90 to 2.10 percent of Mn1; p is less than or equal to 0.0080 percent; s0.035% -0.055%; 0.50 to 0.60 percent of Cr; v0.10% -0.20%; 0.03-0.05% of Ti; 0.015 to 0.035 percent of Al0.015; 0.006 percent to 0.008 percent of N; o is less than or equal to 0.001 percent, and the balance is iron and impurities;
the tensile strength of the material after forging of the martensite/martensite non-quenched and tempered steel reaches 1300 MPa.
Preferably, the composition further comprises 0.01-0.05% of any one or the sum of two of Nb and B by mass percentage.
Preferably, the mass percentages of the V, Ti, Nb or B elements in the various compositions satisfy the following relation: v (%) +2Ti (%) +4Nb (B) (%) -0.50, wherein V (%), Ti (%) represent the mass percent of V and Ti respectively; nb (B) (%) represents the mass percentage of either one or the sum of the Nb and B elements.
Preferably, the bainite/martensite type non-quenched and tempered steel is smelted outside an electric arc furnace or a converter and is cast into a steel ingot or is continuously cast into a blank, and then is forged or rolled into products such as a rod wire and the like.
Preferably, the yield strength of the martensite/martensite type non-quenched and tempered steel reaches 900MPa, and the reduction of area reaches 50%.
According to the technical scheme provided by the embodiment of the invention, the tensile strength of the novel bainite/martensite type non-quenched and tempered steel can reach 1300MPa, the yield strength can reach 900MPa, and the reduction of area can reach 50%, so that compared with the existing ferrite and pearlite type non-quenched and tempered steel, the bainite/martensite type non-quenched and tempered steel has the advantages of high strength, good toughness and the like, and can be used for replacing the quenched and tempered steel to produce safety parts such as automobile bumpers and the like; has the advantages of energy conservation, environmental protection, low cost and the like.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic scanning electron microscope diagram of a microstructure of an experimental material according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
Example one
The invention provides a 1300MPa grade novel bainite/martensite non-quenched and tempered steel which can be used for manufacturing parts such as automobile bumpers with tensile strength of more than 1300 MPa.
The 1300MPa grade novel bainite/martensite non-quenched and tempered steel comprises the following components in percentage by mass: 0.20 to 0.25 percent of C; 0.40 to 0.50 percent of Si; 1.90 to 2.10 percent of Mn1; p is less than or equal to 0.0080 percent; s0.035% -0.055%; 0.50 to 0.60 percent of Cr; v0.10% -0.20%; 0.03-0.05% of Ti0.03; 0.015 to 0.035 percent of Al; 0.006 percent to 0.008 percent of N; less than or equal to 0.001 percent of O, and the balance of iron and inevitable impurities.
Preferably, the composition of the non-tempered steel further comprises: 0.01-0.05% of Nb and B or the sum of the two.
Preferably, the mass percentage of the V, Ti, Nb or B element in the composition of the non-quenched and tempered steel satisfies the relation: v (%) +2Ti (%) +4Nb (B) (%) -0.20-0.50. Wherein V (%), Ti (%) represent the mass percentages of V and Ti, respectively; nb (B) (%) represents the mass percentage of either one or the sum of the Nb and B elements.
Preferably, the tensile strength of the material after the non-quenched and tempered steel is forged can reach 1300MPa, the yield strength can reach 900MPa, and the reduction of area can reach 50%.
The function and the proportion of each element in the technical scheme of the invention are as follows:
c: in order to obtain the required strength level after forging, the C content must be above 0.20%; however, since increasing the C content greatly impairs the ductility, weldability, weather resistance and cold workability of the steel, the C content should be controlled to 0.25% or less.
Si: deoxidizing agents commonly used in steel; si element can shift the C curve to the right, and the hardenability of the steel is increased. The Si content and the C content influence the structure type of the novel Mn-Si-Cr bainite steel after austenitizing and air-cooling. When the content of C is 0.2-0.3% and Si is less than 0.75%, air cooling to obtain a bainite/martensite complex phase structure of the lower bainite; when Si is more than 1.3 percent, the Si has obvious effect of inhibiting carbide precipitation, and a non-carbide bainite/martensite multiphase structure is obtained by air cooling. Therefore, the Si content is controlled to be 0.40-0.50%.
Mn: is an effective element for deoxidation and desulfurization, and can also improve the hardenability and strength of the steel. In the process of cooling the super-cooled austenite, Mn element is enriched at a ferrite/austenite interface to form a concentration peak, phase boundary migration is delayed under the influence of dragging and similar dragging effects of the Mn element, the driving force of bainite phase transformation is reduced, the bainite transformation temperature is reduced, the phase transformation temperature of lath bainite is reduced, and the bainite with fine microstructures such as lath bainite and membranous martensite island is obtained during continuous cooling. When the Mn content in the non-tempered steel exceeds 1.50 to 1.60%, the formation of a bainite structure is promoted, and thus the Mn content is controlled to 1.90 to 2.10%.
P: p can form micro segregation when molten steel is solidified, and then is partially gathered at a grain boundary when the molten steel is heated at high temperature, so that the brittleness of the steel is obviously increased. In addition, the reduction of the P content reduces the deformation resistance of the steel, so the P content is controlled to be less than 0.008%.
S: in order to improve the cutting processing performance of the microalloy non-tempered steel, a proper amount of S element can be added under the condition of not damaging the plasticity and the toughness. S forms inclusions in the steel which are strong to the cutting work. Under certain conditions, S can improve the toughness of the non-tempered steel. Therefore, the content of S is controlled to be 0.035 to 0.055 percent.
Cr: the hardenability of the steel can be effectively improved to obtain the required high strength; cr can greatly reduce the Bs point, can obtain a certain amount of bainite in the air cooling process, and can prevent cracking caused by too fast cooling speed. And C and Cr act together to further reduce the Bs point, ensure that granular bainite and upper bainite are avoided as much as possible in the air cooling process, obtain a lower bainite structure and refine the size of the bainite, and further increase the strength and toughness of the bainite ferrite matrix. Therefore, the Cr content is controlled to be 0.50-0.60%.
V, Ti: both V and Ti belong to strong carbonitride forming elements, and influence the structure and properties of steel through solute dragging, precipitation strengthening, grain refinement and the like. The carbonitride of Ti is relatively excellent in thermal stability in steel, acts to strongly inhibit the migration of austenite grain boundaries, and can serve as a core for precipitation nucleation of other carbides. The solid solubility of V in steel is the largest, and the dispersed V fine precipitates play a remarkable precipitation strengthening role and are simultaneously used as ferrite nucleation cores to refine ferrite grains. Therefore, the content of V is controlled to be 0.10-0.20%;
ti: the effect is similar to V;
nb: the function is similar to V, Ti;
b: the hardenability of the steel is obviously improved, the pearlite transformation is delayed, and the total bainite structure can be obtained in a quite large cooling speed range. In addition, B can promote deformation-induced precipitation of other microalloy elements such as Nb;
n: n forms V (N, C), AlN, TiN, Nb (N, C) and the like with V, Al, Ti, Nb and the like, and mainly plays roles of strengthening precipitation strengthening effect and refining crystal grains in the unconditioned steel, so that the content of N is controlled to be 0.006-0.008%.
Al: AlN formed by Al and N can effectively prevent the coarsening of crystal grains and improve the toughness of the steel. Therefore, the Al content is controlled to be 0.015-0.035%.
In addition, in order to obtain a bainite/martensite structure and further obtain excellent mechanical properties, a large number of research and analysis show that elements such as V, Ti, Nb or B need to be added in a proper compound manner, namely the content of the elements also needs to satisfy the parameter theta relational expression: v (%) +2Ti (%) +4Nb (B) (%) -0.20-0.50. Theta ═ theta
V (%) +2Ti (%) +4Nb (B) (%), when the value of θ is less than 0.20, excellent mechanical properties cannot be obtained although the contents of individual V, Ti, Nb or B elements may be all within the above-mentioned optimum ranges; when the value of θ is greater than 0.50, the effect is saturated and the cost of steel is increased.
In specific production application, the non-quenched and tempered steel can be smelted by an electric arc furnace or a converter and external refining, cast into a steel ingot or continuously cast into a blank, and then forged or rolled into products such as rods, wires and the like.
The technical scheme of the invention is as follows:
(1) adding microalloying element V, Ti, etc. can obviously improve the transformation point (A) of Mn-Cr series bainite non-quenched and tempered steel1、A3) The method is beneficial to expanding the medium-temperature and low-temperature phase transformation areas of the material and increasing the cooling speed range of medium-temperature and low-temperature phase transformation, namely is beneficial to the generation of bainite and martensite;
(2) v (C, N), TiN and the like which are not dissolved or precipitated in the austenitizing heating and cooling process of micro-alloying elements such as V, Ti, Nb and the like are used as nucleation particles in the crystal core, so that the generation of bainite at a higher cooling speed can be promoted;
(3) the hardness and strength level of the material are improved by utilizing the fine grain strengthening and precipitation strengthening effects of microalloyed V, Ti, Nb and the like, so that good mechanical properties are obtained.
Example two
Sample preparation:
according to the designed chemical composition range, 7 furnaces of the steel of the invention and 7 furnaces of the comparison steel are smelted on a 110kg vacuum induction furnace, and the specific chemical compositions are shown in Table 2, wherein furnace numbers 1-7 are the steel of the invention, and furnace numbers 8-14 are the comparison steel. The experimental materials are all smelted into 110kg steel ingots by a vacuum induction furnace, then forged into materials, and the forged experimental materials are processed into samples required by experiments. In the specific production process, the corresponding steel can be obtained by using the corresponding preparation process.
And (3) performance testing:
and casting the molten steel into ingots, and forging the ingots into bars. Samples were taken from the rods and processed into standard room temperature tensile specimens (l)0＝5d0，d0＝5mm)。
The specimens were subjected to tensile testing at room temperature and the results are shown in Table 3.
As can be seen from Table 3, the steel of the present invention can obtain tensile strength of more than 1300MPa after 2 processes of forging treatment, and has good plasticity, and the experimental material has higher strength after the process b treatment. Compared with the comparative steel, the mechanical properties of the steel of the invention are obviously improved under the same treatment process.
TABLE 2 chemical composition (in weight percent) of examples of the present invention
| Furnace number | C | Si | Mn | P | S | Al | Cr | V | Ti | Nb | B | N | O | Fe |
| 1 | 0.20 | 0.42 | 1.95 | 0.0075 | 0.038 | 0.020 | 0.51 | 0.19 | 0.32 | — | — | 0.006 | ≤0.001 | Surplus |
| 2 | 0.22 | 0.46 | 2.02 | 0.0080 | 0.040 | 0.024 | 0.59 | 0.15 | 0.38 | — | — | 0.006 | ≤0.001 | Surplus |
| 3 | 0.24 | 0.48 | 1.99 | 0.0060 | 0.045 | 0.034 | 0.55 | 0.14 | 0.42 | — | — | 0.007 | ≤0.001 | Surplus |
| 4 | 0.22 | 0.50 | 2.08 | 0.0050 | 0.037 | 0.035 | 0.58 | 0.17 | 0.40 | — | 0.002 | 0.007 | ≤0.001 | Surplus |
| 5 | 0.23 | 0.40 | 1.92 | 0.0065 | 0.050 | 0.027 | 0.56 | 0.16 | 0.48 | 0.02 | — | 0.006 | ≤0.001 | Surplus |
| 6 | 0.25 | 0.45 | 2.10 | 0.0055 | 0.053 | 0.018 | 0.52 | 0.11 | 0.32 | — | — | 0.008 | ≤0.001 | Surplus |
| 7 | 0.22 | 0.48 | 1.99 | 0.0075 | 0.042 | 0.016 | 0.54 | 0.12 | 0.31 | 0.03 | — | 0.006 | ≤0.001 | Surplus |
| 8 | 0.22 | 0.43 | 2.03 | 0.0080 | 0.046 | 0.026 | 0.57 | — | — | — | — | 0.007 | ≤0.001 | Surplus |
| 9 | 0.24 | 0.44 | 2.06 | 0.0065 | 0.038 | 0.022 | 0.52 | — | — | — | — | 0.006 | ≤0.001 | Surplus |
| 10 | 0.22 | 0.41 | 1.94 | 0.0070 | 0.047 | 0.016 | — | 0.14 | — | — | — | 0.008 | ≤0.001 | Surplus |
| 11 | 0.23 | 0.47 | 2.05 | 0.0055 | 0.035 | 0.034 | — | 0.15 | — | — | — | 0.006 | ≤0.001 | Surplus |
| 12 | 0.25 | 0.42 | 1.92 | 0.0060 | 0.039 | 0.029 | — | — | 0.40 | — | — | 0.007 | ≤0.001 | Surplus |
| 13 | 0.21 | 0.45 | 2.0 | 0.0070 | 0.040 | 0.022 | — | — | — | — | — | 0.006 | ≤0.001 | Surplus |
| 14 | 0.20 | 0.40 | 2.01 | 0.0080 | 0.038 | 0.016 | — | — | — | — | — | 0.006 | ≤0.001 | Surplus |
TABLE 3 Strength and plasticity of examples of the invention
Fig. 1 is a schematic scanning electron microscope of a microstructure of an experimental material according to an embodiment of the present invention, where LLB-lower lath-bainite is lower bainite, and GB-granular bainite is granular bainite). As can be seen from FIG. 1, the forged air-cooled structure of the experimental steel is a complex phase morphology of Lower bainite (LLB) and Granular Bainite (GB). The granular bainite is composed of a ferrite matrix and island-like martensite/austenite (M/A) components. The M/A component is a mixture of M + A, and also has single martensite or austenite.
In conclusion, compared with the prior art, the embodiment of the invention provides 1300 MPa-grade novel bainite/martensite non-quenched and tempered steel, which has the advantages of less material alloy elements, no precious alloy elements and low cost; the tempering process is omitted in the preparation process, the forging is air-cooled to room temperature, the cooling speed is not required to be controlled, the production cost is further reduced, the production period is shortened, and the energy conservation and environmental protection are realized; compared with the prior ferrite and pearlite type non-quenched and tempered steel, the steel has the advantages of high strength, good toughness and the like, and can be used for replacing the quenched and tempered steel to produce safety parts such as automobile bumpers and the like.
The tensile strength of the novel bainite/martensite type non-quenched and tempered steel provided by the invention can reach 1300MPa, the yield strength can reach 900MPa, and the reduction of area can reach 50%, compared with the existing ferrite and pearlite type non-quenched and tempered steel, the novel bainite/martensite type non-quenched and tempered steel has the advantages of high strength, good toughness and the like, and can be used for replacing the quenched and tempered steel to produce safety parts such as automobile bumpers and the like; has the advantages of energy conservation, environmental protection, low cost and the like.
Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (2)
1. A bainite/martensite type non-quenched and tempered steel is characterized by comprising the following components in percentage by mass: 0.20 to 0.25 percent of C; 0.40 to 0.50 percent of Si; 1.90 to 2.10 percent of Mn1; p is less than or equal to 0.0080 percent; s0.035% -0.055%; 0.50 to 0.60 percent of Cr; v0.10% -0.20%; 0.03-0.05% of Ti; 0.015 to 0.035 percent of Al; 0.006 percent to 0.008 percent of N; o is less than or equal to 0.001 percent, and one or two of Nb and B with the content sum of 0.01 to 0.05 percent, and the balance of iron and impurities;
and the mass percentages of V, Ti, Nb or B elements in the components satisfy the following relational expression:
0.20≤V(％)+2Ti(％)+4Nb(B)(％)≤0.50，
wherein V (%), Ti (%) represent the mass percentages of V and Ti, respectively; nb (B) (%) represents the mass percentage of either one or the sum of two of Nb and B elements;
b is used for improving the hardenability of the steel and promoting the deformation induced precipitation of other microalloy elements;
the tensile strength of the forged material of the martensite/martensite non-quenched and tempered steel reaches 1300MPa, the yield strength reaches 900MPa, and the reduction of area reaches 50%.
2. The bainite/martensite-type non-heat-treated steel according to claim 1, wherein the bainite/martensite-type non-heat-treated steel is smelted by an electric arc furnace or a converter plus external refining, cast into an ingot or continuously cast into a billet, and then forged or rolled into a rod-wire product.
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