CN113832389B - Cold extrusion round steel and manufacturing method thereof - Google Patents
Cold extrusion round steel and manufacturing method thereof Download PDFInfo
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- 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
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- 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
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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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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Abstract
The invention discloses cold-extruded round steel which contains the following chemical elements in percentage by mass besides Fe: c:0.30 to 0.45%, si:0.10 to 0.50%, mn:1.0 to 1.60%, S:0.005 to 0.030%, al:0.01 to 0.06 percent. In addition, the invention also discloses a manufacturing method of the cold extrusion round steel, which comprises the following steps: smelting and casting; (2) heating; (3) forging or rolling; (4) normalizing: normalizing at 850-900 deg.c and air cooling; (5) spheroidizing annealing: heating to 740-760 ℃ and preserving heat for a period of time, then cooling to 690-710 ℃ at a cooling rate of 5-20 ℃/h and preserving heat for a period of time, then cooling to 650-680 ℃ at a cooling rate of 2-15 ℃/h and preserving heat for a period of time, then cooling to below 500 ℃ at a cooling rate of 5-20 ℃/h, and then discharging and cooling. The cold-extrusion round steel has excellent plasticity and cold-processing characteristics, can be used for cold-extrusion processing of clutch sleeves and the like, and has good popularization prospect and application value.
Description
Technical Field
The invention relates to a metal material and a manufacturing method thereof, in particular to a steel grade and a manufacturing method thereof.
Background
The clutch sleeve is a key part of a manual gear automobile part. With the rapid development of the automobile industry, the demand of the clutch sleeve is high for a long time in the face of a wide automobile market. Because the shape of the clutch sleeve is special, the requirement on the dimensional accuracy is high, if a conventional finish machining process mode after hot forging is adopted, on one hand, the utilization rate of materials is low, on the other hand, the energy consumption required by hot forging is high, the processing cost can be increased, and the environmental pollution can be generated.
Therefore, the part processing enterprise often adopts cold extrusion technique to produce the clutch race, and part cold extrusion technique possesses many-sided advantage: (1) The near-net-shaped body has high size and shape and position precision, and can provide an ideal blank for subsequent high-efficiency and high-precision processing; (2) For the net-shaped parts, a plurality of parts do not need subsequent processing, so that the waste of raw materials is greatly reduced; (3) The production efficiency is high, the energy consumption is low, the manufacturing cost can be effectively reduced, the manufacturing period is shortened, the competitiveness of the product is improved, and the performance and the quality of the precision forming product are greatly improved compared with the product processed by traditional cutting; (4) Compared with the traditional forming process, the part cold extrusion technology has the advantages that the production conditions are improved, and the pollution to the environment is greatly reduced; (5) In the aspect of cold precision forming of the part cold extrusion technology, due to the reduction of heat treatment procedures and the improvement of a non-flash process, the energy consumption and the pollution degree are greatly reduced. Therefore, the cold extrusion technology is more suitable for the future trend of clean manufacturing and green environmental protection, and can create favorable conditions for sustainable development.
However, the cold extrusion technology has high requirements on the plasticity of materials, and part enterprises often have high rejection rate of parts after processing and increase detection cost due to cracking or microcrack initiation in the extrusion process caused by unqualified steel quality.
Based on this, it is desired to obtain a steel material having excellent plasticity and cold working characteristics, which can be effectively applied to cold extrusion working of a clutch sleeve.
Disclosure of Invention
One of the purposes of the invention is to provide the cold-extruded round steel which not only has proper strength, but also has excellent plasticity and cold extrusion performance, has very wide applicability, and has good popularization prospect and application value.
In order to achieve the purpose, the invention provides cold-extruded round steel which contains the following chemical elements in percentage by mass besides Fe:
C：0.30～0.45％、Si：0.10～0.50％、Mn：1.0～1.60％、S：0.005～0.030％、Al：0.01～0.06％。
further, in the cold-extruded round steel of the present invention, the mass percentages of the chemical elements are:
c:0.30 to 0.45%, si:0.10 to 0.50%, mn:1.0 to 1.60%, S:0.005 to 0.030%, al:0.01 to 0.06 percent, and the balance of Fe and other inevitable impurity elements.
In the cold-extruded round steel of the present invention, the design principle of each chemical element is as follows:
c: in the cold-extruded round steel, the C element is added into the steel, so that the hardenability of the steel can be effectively improved, the steel can be ensured to have certain strength and hardness, and the wear resistance of parts prepared by processing the steel can be improved. However, it should be noted that the increased content of C in the steel increases the hardness of the steel, which results in too high strength of the material during subsequent processing and increased wear of the cold extrusion die. If the content of C element in the steel is too low, the steel cannot obtain high tensile strength, which may result in a decrease in wear resistance of parts produced after the steel is processed and a decrease in service life. Based on the above, the mass percent of C in the cold-extruded round steel is controlled between 0.30 and 0.45 percent.
Si: in the cold-extruded round steel, si can replace Fe atoms in the steel in a replacement mode, so that dislocation movement is hindered, and the strength of the steel is improved. In addition, si element can also reduce the diffusion capacity of C in ferrite, so that proper amount of Si element can effectively avoid forming coarse carbide to precipitate at the defect during spheroidizing annealing. However, it should be noted that too high a content of Si element in the steel may lower the plasticity of the steel. Therefore, the mass percent of Si in the cold-extruded round steel is controlled between 0.10 and 0.50 percent.
Mn: in the cold-extruded round steel, when a certain amount of S element exists in the steel, the Mn element and the S easily form plastic MnS, so that the improvement of the cutting performance in the subsequent turning process can be greatly facilitated. It should be noted that the high content of Mn element in the steel may increase the strength and hardness of the steel, and may increase the loss of the die during the subsequent cold extrusion process. Therefore, in order to improve the free-cutting performance of the material and simultaneously avoid higher strength of steel, the mass percent of Mn in the cold-extruded round steel is controlled to be between 1.0 and 1.60 percent.
S: in the cold-extruded round steel, a proper amount of S element is added into the steel, and the S element and Mn element can form MnS to improve the cutting performance, so that the phenomenon of knife sticking in the subsequent finish machining process is avoided. Based on the above, the mass percent of S in the cold-extruded round steel is controlled to be 0.005-0.030%.
Al: in the cold-extruded round steel, al element can form fine AlN precipitation in the steel-making process, and the Al element can inhibit austenite grains from growing in the subsequent cooling process, so that the aims of refining the austenite grains and improving the toughness of the steel at low temperature are fulfilled. However, it should be noted that too high an Al element content in the steel results in the formation of large Al oxides, which makes ultrasonic flaw detection of the steel undesirable, and coarse alumina inclusions deteriorate the fatigue properties of the steel. Based on the above, in order to make Al element effectively exert the beneficial effects in the invention, the mass percent of Al in the cold-extruded round steel is controlled to be 0.01-0.06%.
Further, the cold-extruded round steel according to the present invention further includes at least one of the following elements: cr is more than 0 and less than or equal to 0.10 percent, mo is more than 0 and less than or equal to 0.20 percent, ni is more than 0 and less than or equal to 0.20 percent, cu is more than 0 and less than or equal to 0.20 percent, V is more than 0 and less than or equal to 0.12 percent, ca is more than 0 and less than or equal to 0.005 percent, and Ti is more than 0 and less than or equal to 0.008 percent.
In the above technical solution, the Cr, mo, ni, cu, V, ca, and Ti may further improve the performance of the cold-extruded round steel of the present invention, and the design principle of the chemical elements is as follows:
cr: in the cold-extruded round steel, cr element is added into the steel, so that the diffusion type phase change of the steel can be inhibited, and the diffusion nucleation in the spheroidization process is not facilitated. If the Cr element content in the steel is too high, coarse carbides are formed, and the cold formability is deteriorated. Therefore, the mass percent of Cr in the cold-extruded round steel can be controlled to be more than 0 and less than or equal to 0.10 percent.
Mo: in the cold-extruded round steel, mo element mainly exists in the steel in a solid solution form, which can play a solid solution strengthening effect, and can form fine carbides during tempering at a higher temperature, so that carbide nucleation of the steel in a spheroidizing annealing process is improved, and nucleation time in the spheroidizing annealing process is reduced. However, it should be noted that Mo is a precious alloy element, and the addition of Mo in steel at a higher content leads to an increase in production cost. Therefore, the mass percent of Mo in the cold-extruded round steel can be controlled to be more than 0 and less than or equal to 0.20 percent.
Ni: in the cold-extruded round steel of the present invention, the Ni element exists in solid solution in the steel, which can effectively improve the strength of the steel. However, it should be noted that too high Ni content in steel will increase the die wear during cold extrusion, and Ni is an austenitizing element, which will result in too high residual austenite content in steel, which is not conducive to spheroidizing of carbides. Therefore, in order to ensure the plasticity and proper strength of the steel, the mass percent of Ni in the cold-extruded round steel is controlled to be more than 0 and less than or equal to 0.20 percent.
V: in the cold-extruded round steel, the V element and the C can form VC, and the fine VC can form nucleation points in the spheroidizing annealing process, so that the inoculation time is reduced, the annealing time is shortened, and the cost is reduced. If the contents of C and V elements in the steel are high, coarse VC particles are formed, and the plasticity of the steel is reduced. Therefore, the cold-extruded round steel can control the mass percent of V to be more than 0 and less than or equal to 0.12 percent.
Cu: in the cold-extruded round steel, cu can participate in the smelting process of steel, and considering that the melting point of Cu is low, if the mass percentage of the Cu in the steel is too high, the Cu can be enriched in a grain boundary in the heating austenitizing process, so that the grain boundary is weakened to cause cracking. Therefore, the mass percent of Cu in the cold-extruded round steel can be controlled to be more than 0 and less than or equal to 0.20 percent.
Ca: in the cold-extruded round steel, a proper amount of Ca element is added into the steel to form CaS, so that the size and the appearance of inclusions are improved, and the impact toughness of the steel is improved. However, it should be noted that the Ca element in the steel is not too high. Therefore, the mass percent of Ca in the cold-extruded round steel is more than 0 and less than or equal to 0.005 percent.
Ti: in the cold-extruded round steel, ti element can form corresponding compounds with C and N in the steel, wherein the formation temperature of TiN is more than 1400 ℃, and TiN is usually precipitated in a liquid phase or delta ferrite, thereby realizing the purpose of refining austenite grains. However, it should be noted that if the content of Ti element in the steel is too high, coarse TiN precipitates are formed, thereby deteriorating the fatigue properties of the steel. Therefore, the mass percentage of Ti in the cold-extruded round steel can be controlled to be more than 0 and less than or equal to 0.008 percent.
In addition, the addition of the above elements can increase the cost of the material, and in the technical scheme of the invention, at least one of the above elements can be preferably added in consideration of the combination of the performance and the cost control.
Furthermore, in the cold-extruded round steel, P is less than or equal to 0.015 percent, N is less than or equal to 0.0120 percent, and O is less than or equal to 0.0030 percent of other inevitable impurities.
In the technical scheme, in the cold-extruded round steel, P, N and O are inevitable impurity elements in the steel. The P element in steel is segregated at grain boundaries, reducing the bonding energy of the grain boundaries, and deteriorating the plasticity of the steel.
The coexistence of P and Mn can aggravate the tempering brittleness of steel, and the P element which is segregated in the grain boundary can lead the steel to generate crystal fracture when the steel is under the action of impact load, so that a large cleavage plane is formed, and the plasticity of the steel is deteriorated. Therefore, in order to avoid the brittleness of the steel from becoming high, in the cold-extruded round steel of the present invention, the mass percentage of P is controlled to be P less than or equal to 0.015%.
Accordingly, although the N element can form AlN or TiN in the steel and can play a role of refining austenite grains, the increase of the content of the N element in the steel can lead to the increase of the enrichment amount of the N element at the defect position, and simultaneously, coarse nitride precipitation particles can be formed, and the fatigue life of the steel is influenced. Therefore, the mass percent of N element is required to be controlled to be less than or equal to 0.0120 percent.
The impurity element O can form Al with Al and Ti elements in the steel 2 O 3 And TiO, so that in order to ensure the uniformity of the steel structure, the mass percent of O in the cold-extruded round steel is controlled to be less than or equal to 0.0030 percent.
Further, in the cold-extruded round steel according to the present invention, the microstructure thereof is ferrite + spherical carbide.
Further, in the cold-extruded round steel of the present invention, the performance satisfies at least one of the following: the yield strength is 300-400MPa, the tensile strength is 550-650MPa, the elongation is more than or equal to 35%, and the reduction of area is more than or equal to 60%.
Correspondingly, the invention also aims to provide a method for manufacturing the cold-extruded round steel, the cold-extruded round steel manufactured by the method has the yield strength of 300-400MPa, the tensile strength of 550-650MPa, the elongation of more than or equal to 35 percent and the reduction of area of more than or equal to 60 percent, and has excellent plasticity and cold processing characteristics.
In order to achieve the above object, the present invention provides the above method for manufacturing cold-extruded round steel, comprising the steps of:
(1) Smelting and casting;
(2) Heating;
(3) Forging or rolling;
(4) Normalizing: normalizing at 850-900 deg.c and air cooling to room temperature;
(5) Spheroidizing annealing: heating to 740-760 ℃ and preserving heat for a period of time, then cooling to 690-710 ℃ at a cooling rate of 5-20 ℃/h and preserving heat for a period of time, then cooling to 650-680 ℃ at a cooling rate of 2-15 ℃/h and preserving heat for a period of time, then cooling to below 500 ℃ at a cooling rate of 5-20 ℃/h, and then discharging and cooling.
According to the manufacturing method of the cold-extruded round steel, the process conditions, particularly the heat treatment process parameters, are controlled, the forged or rolled bar is controlled to adopt the spheroidizing annealing process after normalizing, so that the cold-extruded round steel manufactured by the manufacturing method of the invention obtains a matrix structure of ferrite and spherical carbide, a large amount of ferrite is arranged on the matrix, the cold-extruded round steel has good plasticity, the internal stress of steel is eliminated, and the cold-extruded round steel has good tissue uniformity.
It should be noted that, in the step (1) of the manufacturing method of the present invention, an electric furnace or a converter may be used for smelting in the smelting process. Accordingly, in the casting process, die casting or continuous casting may be employed.
Further, in step (3), a forging or rolling process may be employed. If the forging process is adopted, the round steel can be directly forged to the final size of the round steel. If the rolling process is adopted, the billet can also be directly rolled to the final specification. In some embodiments, during the rolling process, the billet may be rolled to a specified intermediate billet size, and then the obtained intermediate billet is heated and rolled to obtain the final finished product size.
In the above-mentioned means, in the step (4), the normalizing temperature is controlled to 850 to 900 ℃, and then air cooling is performed after normalizing. It should be noted that the normalization can effectively ensure the uniformity of the round steel structure.
Further, in the production method of the present invention, in the step (2), the heating temperature is controlled to be 1080 to 1200 ℃.
In the technical scheme, in the heating process of the step (2), the steel is heated to austenitize at a heating temperature of 1080-1200 ℃, and V elements and carbonitrides in the steel and carbides of Cr and Mo can be partially or completely dissolved in austenite, so that in the subsequent forging or rolling and cooling processes, the V elements can form fine carbonitrides, and the austenite grain boundaries are subjected to nail rolling to play a role in refining the rolled structure of the steel.
Further, in the manufacturing method of the present invention, in the step (3), the finish rolling or finish forging temperature is 850 to 1000 ℃.
Further, in the manufacturing method of the invention, in the step (5), the temperature is heated to 740-760 ℃ and is preserved for more than 4 hours, then the temperature is cooled to 690-710 ℃ at the cooling rate of 5-20 ℃/h and is preserved for more than 4 hours, then the temperature is cooled to 650-680 ℃ at the cooling rate of 2-15 ℃/h and is preserved for more than 3 hours, then the temperature is cooled to below 500 ℃ at the cooling rate of 5-20 ℃/h, and then the product is taken out of the furnace and cooled.
Compared with the prior art, the cold-extruded round steel and the manufacturing method thereof have the advantages and beneficial effects that:
in conclusion, the invention can be seen that through reasonable chemical composition design, the influence of various alloy elements on phase change and microstructure is fully utilized, and a specific heat treatment process is matched, so that a uniform ferrite + spherical carbide matrix structure is formed. Meanwhile, the content of P, N and O is effectively controlled, and the obtained cold extrusion round steel has proper strength, excellent plasticity, elongation and the like.
The cold extrusion round steel has good plasticity and section shrinkage rate at low temperature and excellent cold extrusion performance. The cold-extruded round steel has the yield strength of 300-400MPa, the tensile strength of 550-650MPa, the elongation of more than or equal to 35 percent and the reduction of area of more than or equal to 60 percent, and has excellent plasticity and cold processing characteristics.
In addition, the cold-extruded round steel has reasonable chemical components and process design, wide process window, can realize batch commercial production on a bar or plate production line, and has good popularization prospect and application value.
Drawings
Fig. 1 is a microstructure photograph of the cold-extruded round steel of example 4 under an optical microscope.
Fig. 2 is an SEM image of cold-extruded round steel of example 4.
Detailed Description
The cold-extruded round steel and the method for manufacturing the same according to the present invention will be further explained and illustrated with reference to the following specific examples and drawings, which, however, should not be construed as unduly limiting the technical scope of the invention.
Examples 1 to 6
The cold-extruded round bars of examples 1 to 6 were all produced by the following steps:
(1) Smelting and casting by using an electric furnace or a converter according to chemical components shown in the table 1;
(2) Heating: the heating temperature is controlled to be 1080-1200 ℃;
(3) Forging or rolling: the final rolling or forging temperature is 850-1000 ℃;
(4) Normalizing: keeping the normalizing temperature at 850-900 ℃ for a period of time, and then cooling the mixture to room temperature in air;
(5) Spheroidizing annealing: heating to 740-760 ℃ and preserving heat for a period of time, then cooling to 690-710 ℃ at a cooling rate of 5-20 ℃/h and preserving heat for a period of time, then cooling to 650-680 ℃ at a cooling rate of 2-15 ℃/h and preserving heat for a period of time, then cooling to below 500 ℃ at a cooling rate of 5-20 ℃/h, and then discharging and cooling.
In examples 1 to 6, the billet was rolled in step (3) by a rolling process. In the rolling process, the finishing temperature is controlled to be 850-1000 ℃ in the examples 1-6, the billet is firstly rolled into an intermediate billet with the size specification of 215 × 215mm, then the intermediate billet is heated again, and after the intermediate billet is taken out of a heating furnace, the intermediate billet is rolled again to be rolled into a finished product round steel with the specification of phi 55 mm.
Of course, in some other embodiments, the finishing temperature can be controlled to be 850-1000 ℃ to directly roll the finished round steel. In other embodiments, the finished round steel can be directly forged by adopting a forging process and controlling the forging temperature to be 850-1000 ℃.
Correspondingly, in the step (3) of the embodiment 6 of the invention, a forging process is adopted, and in the embodiment 6, the finished round steel with the specification of phi 55mm is directly forged by controlling the finish forging temperature to be 850-1000 ℃.
Table 1 shows the mass percentages of the chemical elements in the cold-extruded round bars of examples 1 to 6.
TABLE 1 (wt%, balance Fe and other unavoidable impurities other than P, N and O)
| Number of | C | Si | Mn | P | S | Cr | Mo | Ni | V | Al | Ti | Ca | N | O | Cu |
| Example 1 | 0.30 | 0.50 | 1.60 | 0.015 | 0.028 | 0.02 | 0.02 | 0.02 | 0.10 | 0.01 | 0.005 | 0.005 | 0.0118 | 0.0030 | 0.19 |
| Example 2 | 0.350 | 0.40 | 1.40 | 0.011 | 0.023 | 0.04 | 0.06 | 0.07 | 0.08 | 0.03 | 0.006 | 0.003 | 0.0094 | 0.0013 | 0.16 |
| Example 3 | 0.400 | 0.30 | 1.20 | 0.009 | 0.016 | 0.05 | 0.10 | 0.13 | 0.05 | 0.05 | 0.002 | 0.002 | 0.0045 | 0.0022 | 0.13 |
| Example 4 | 0.450 | 0.11 | 1.0 | 0.007 | 0.012 | 0.06 | 0.15 | 0.18 | 0.02 | 0.06 | 0.0015 | 0.003 | 0.0017 | 0.0025 | 0.09 |
| Example 5 | 0.42 | 0.20 | 1.1 | 0.006 | 0.009 | 0.08 | 0.20 | 0.05 | 0.06 | 0.02 | 0.003 | 0.002 | 0.0050 | 0.0012 | 0.06 |
| Example 6 | 0.38 | 0.3 | 1.50 | 0.005 | 0.006 | 0 | 0 | 0 | 0 | 0.04 | 0 | 0. | 0.0066 | 0.0016 | 0 |
Specific process parameters for the cold-extruded round bars of examples 1-6 are listed in tables 2-1 and 2-2.
Table 2-1.
Table 2-2.
The cold-extruded round steels of examples 1 to 6 were subjected to various performance tests, and the test results are shown in Table 3.
Table 3 shows the results of the mechanical property tests of the cold-extruded round steels of examples 1 to 6.
Table 3.
As can be seen from Table 3, the cold-extruded round steel in the embodiments 1 to 6 of the invention has excellent mechanical properties, the yield strength of each embodiment is 300 to 400MPa, the tensile strength is 550 to 650MPa, the elongation is more than or equal to 35 percent, and the reduction of area is more than or equal to 60 percent. The cold-extruded round steel of each example is excellent in mechanical properties, has good plasticity and reduction of area at low temperature, and has excellent cold-working characteristics.
Fig. 1 is a microstructure photograph of the cold-extruded round steel of example 4 under an optical microscope.
Fig. 2 is an SEM image photograph of the cold-extruded round steel of example 4.
As can be seen from fig. 1 and 2, in the cold-extruded round steel of example 4 of the present invention, the microstructure of the cold-extruded round steel is spherical carbide and ferrite.
In conclusion, the invention can be seen that through reasonable chemical composition design, the influence of various alloy elements on phase change and microstructure is fully utilized, and a specific heat treatment process is matched, so that a uniform ferrite + spherical carbide matrix structure is formed. Meanwhile, the invention effectively controls the contents of P, N and O, and effectively ensures that the steel has proper strength, excellent plasticity, elongation and the like. The cold extrusion round steel has good plasticity and section shrinkage rate at low temperature and excellent cold extrusion performance. The cold-extruded round steel has the yield strength of 300-400MPa, the tensile strength of 550-650MPa, the elongation of more than or equal to 35 percent and the reduction of area of more than or equal to 60 percent, and has excellent plasticity and cold processing characteristics.
The cold-extruded round steel has reasonable chemical components and process design and loose process window, can realize batch commercial production on a bar or plate production line, and has good popularization prospect and application value.
In addition, the combination of the features in the present application is not limited to the combination described in the claims of the present application or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradictory to each other.
It should also be noted that the above list is only specific examples of the present invention, and it is obvious that the present invention is not limited to the above examples, and many similar variations are possible. All modifications which would occur to one skilled in the art and which are, therefore, directly derived or suggested from the disclosure herein are deemed to be within the scope of the present invention.
Claims (8)
1. The cold-extruded round steel is characterized by comprising the following chemical elements in percentage by mass in addition to Fe:
C：0.30～0.45％、Si：0.10～0.50％、Mn：1.0～1.60％、S：0.005～0.030％、Al：0.01～0.06％；
the microstructure of the cold-extruded round steel is ferrite and spherical carbide;
the cold extrusion round steel adopts the following process in the manufacturing process:
normalizing: normalizing at 850-900 deg.c and air cooling to room temperature;
spheroidizing annealing: heating to 740-760 deg.C, keeping the temperature for more than 4 hours, cooling to 690-710 deg.C at a cooling rate of 5-20 deg.C/h, keeping the temperature for more than 4 hours, cooling to 650-680 deg.C at a cooling rate of 2-15 deg.C/h, keeping the temperature for more than 3 hours, cooling to below 500 deg.C at a cooling rate of 5-20 deg.C/h, and cooling.
2. The cold-extruded round steel of claim 1, wherein the chemical elements comprise, by mass:
c:0.30 to 0.45%, si:0.10 to 0.50%, mn:1.0 to 1.60%, S:0.005 to 0.030%, al:0.01 to 0.06 percent, and the balance of Fe and other inevitable impurity elements.
3. A cold-extruded round bar as claimed in claim 1 or 2, further comprising at least one of the following elements:
0＜Cr≤0.10％、0＜Mo≤0.20％、0＜Ni≤0.20％、0＜Cu≤0.20％、0＜V≤0.12％、0＜Ca≤0.005％、0＜Ti≤0.008％。
4. the cold-extruded round steel as claimed in claim 2, wherein P is 0.015% or less, N is 0.0120% or less, and O is 0.0030% or less of the other unavoidable impurities.
5. A cold-extruded round bar as claimed in claim 1 or 2, wherein the properties satisfy at least one of the following: the yield strength is 300-400MPa, the tensile strength is 550-650MPa, the elongation is more than or equal to 35%, and the reduction of area is more than or equal to 60%.
6. A method of manufacturing cold-extruded round steel as claimed in any one of claims 1 to 5, comprising the steps of:
(1) Smelting and casting;
(2) Heating;
(3) Forging or rolling;
(4) Normalizing: normalizing at 850-900 deg.c and air cooling to room temperature;
(5) Spheroidizing annealing: heating to 740-760 deg.C, keeping the temperature for more than 4 hours, cooling to 690-710 deg.C at a cooling rate of 5-20 deg.C/h, keeping the temperature for more than 4 hours, cooling to 650-680 deg.C at a cooling rate of 2-15 deg.C/h, keeping the temperature for more than 3 hours, cooling to below 500 deg.C at a cooling rate of 5-20 deg.C/h, and cooling.
7. The production method according to claim 6, wherein in the step (2), the heating temperature is controlled to be 1080 to 1200 ℃.
8. The manufacturing method according to claim 6, wherein, in the step (3), the finish rolling or finish forging temperature is 850 to 1000 ℃.
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