CN114836681B - High-strength seamless steel pipe with good fatigue resistance and manufacturing method thereof - Google Patents
High-strength seamless steel pipe with good fatigue resistance and manufacturing method thereof Download PDFInfo
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
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- C21D1/26—Methods of annealing
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
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- C21D1/28—Normalising
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- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
- C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
- C21D9/085—Cooling or quenching
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- 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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses a high-strength seamless steel pipe with good fatigue resistance, which contains the following chemical elements in percentage by mass besides Fe and unavoidable impurities: c:0.28 to 0.38 percent, si is less than or equal to 0.35 percent, mn:0.5 to 1.0 percent, cr:0.6 to 1.6 percent, mo:0.1 to 0.35 percent, N:0.0035 to 0.0085 percent, al:0.020 to 0.055 percent, ca:0.0005 to 0.005 percent. In addition, the invention also discloses a manufacturing method of the high-strength seamless steel pipe, which comprises the following steps: (1) preparing a tube blank; (2) Heating, perforating, hot rolling and sizing to obtain a hot rolled pipe; (3) intermediate heat treatment; (4) cold drawing or cold rolling; and (5) normalizing or annealing heat treatment.
Description
Technical Field
The present invention relates to a seamless steel pipe and a method for manufacturing the same, and more particularly, to a high-strength seamless steel pipe and a method for manufacturing the same.
Background
In recent years, along with the strictness of environmental protection regulations and policies in China, the requirements of markets and users on energy conservation and emission reduction of automobiles are higher and higher, in order to achieve the maximum light weight, in addition to adopting high-strength steel and light materials for main automobile bodies, automobile parts such as driving shaft products which occupy smaller weight in the whole automobile are also brought into weight reduction rows, and hollow pipes are increasingly used for replacing solid bars and forging materials.
The driving shaft and other parts of the automobile play a role of transmitting the engine torque to the driving wheels, and are very important safety parts. The driving shaft needs to bear great torsion moment, traction force, braking force and the like from wheels, and the bearing force comprises longitudinal force, lateral force, vertical force, vibration impact force and the like, so that the material is required to have strong strength and plasticity to ensure sufficient fatigue resistance. In addition, along with the improvement of the living standard of people, the comfort level of the automobile in the driving process is also required to be higher and higher, so that the material design is light in weight and meanwhile the rigidity and the like of the material are required to be considered, so that the anti-seismic property of the automobile is improved, and the effect of noise reduction is achieved.
Therefore, the traditional mode of producing the automobile driving shaft by friction stir welding is gradually replaced by new processes such as cold die forging and the like, and the hollow steel pipe material is integrally processed into a special shape which is more beneficial to noise reduction, middle diameter expansion and thinning and two-end diameter reduction and thickening, and is beneficial to processing of end splines, so that the hollow steel pipe material also needs to have good cold processing performance.
Chinese patent document publication No. CN104962838A, publication No. 2015, 10 months and 7 days, entitled "high-strength steel, high-strength plastic seamless steel pipe for automotive transmission half shaft and manufacturing method thereof" discloses a high-strength plastic seamless steel pipe, which comprises the chemical components: c:0.07 to 0.15 percent, si:0.1 to 1.0 percent, mn:2.0 to 2.6 percent, ni:0.05 to 0.6 percent, cr:0.2 to 1.0 percent, mo:0.1 to 0.6 percent, B:0.001-0.006% Cu 0.05-0.50%; 0.015 to 0.060 percent of Al; nb 0.02-0.1%; v is 0.02-0.15%, the steel pipe is designed to be low in C, low in strength, favorable for welding and suitable for automobile half shafts produced by friction stir welding.
Chinese patent document publication No. CN1950532a, publication No. 2007, 4-month and 18-day, entitled "seamless steel pipe and method for producing same", discloses a slit steel pipe and method for producing same, comprising the chemical components in mass percent: c:0.30 to 0.50 percent, si is less than or equal to 0.50 percent, mn:0.3 to 2.0 percent, P is less than or equal to 0.025 percent, S is less than or equal to 0.005 percent, cr:0.15 to 1.0 percent, 0.001 to 0.050 percent of Al; ti: 0.005-0.05%, N is less than or equal to 0.02%, B is 0.0005-0.01%, and O is less than or equal to 0.0050%; and Beff is greater than or equal to 0.0001: wherein a) when neff=n-14×ti/47.9+.0, beff=b-10.8 (N-14×ti/47.9)/14; b) Beff=b. The material has excellent cold workability, hardenability, toughness, and torsional fatigue strength when neff=n-14×ti/47.9< 0. The invention uses high C, mn and Cr and controls the proportion of Ti/B/N to achieve high strength and hardenability, but too high C is easy to generate quenching cracks and grinding cracks in the hardening and tempering process.
Based on the defects and shortcomings in the prior art, the invention is expected to obtain the high-strength seamless steel pipe with good fatigue resistance, and the high-strength seamless steel pipe not only has good room temperature mechanical property, cold processing property and good torsion fatigue resistance life, but also has excellent toughness, and can be effectively applied to parts bearing high torsion load, such as automobile driving shafts and the like.
Disclosure of Invention
The invention aims to provide a high-strength seamless steel pipe with good fatigue resistance, which has good room temperature mechanical property, cold processing property and torsion fatigue resistance life, has excellent toughness, does not crack in the cold processing process and does not crack in the quenching and tempering process, is particularly suitable for parts bearing high torsion load such as automobile driving shafts, and has very wide application prospect.
In order to achieve the above object, the present invention provides a high-strength seamless steel pipe having excellent fatigue resistance, which contains the following chemical elements in mass percent in addition to Fe and unavoidable impurities:
C：0.28～0.38％，Si≤0.35％，Mn：0.5～1.0％，Cr：0.6～1.6％，Mo：0.1～0.35％，N：0.0035～0.0085％,Al：0.020～0.055％,Ca：0.0005～0.005％。
further, in the high-strength seamless steel pipe with good fatigue resistance, the mass percentage of each chemical element is as follows:
c: 0.28-0.38%, si is more than 0 and less than or equal to 0.35%, mn:0.5 to 1.0 percent, cr:0.6 to 1.6 percent, mo:0.1 to 0.35 percent, N:0.0035 to 0.0085 percent, al:0.020 to 0.055 percent, ca:0.0005 to 0.005 percent; the balance being Fe and unavoidable impurities.
In the high-strength seamless steel pipe with good fatigue resistance, the design principle of each chemical element is specifically as follows:
c: in the high-strength seamless steel pipe with good fatigue resistance, the content of the element C is improved to be beneficial to improving the strength and fatigue resistance of the material, but the content of the element C in the steel is not too high, and when the content of the element C in the steel is too high, the toughness and plasticity of the steel are reduced, cold working is not facilitated, processing cracks are easy to occur, and decarburization control is difficult. Therefore, in order to ensure the quenching hardness and the hardenability of the material, ensure the hardenability of the material, reduce the quenching crack sensitivity and ensure the cold processing performance, the mass percent of C in the high-strength seamless steel pipe with good fatigue resistance is controlled between 0.28 and 0.38 percent.
Of course, in some preferred embodiments, the mass percentage of C may be preferably controlled between 0.31 and 0.36% for better implementation.
Si: in the high-strength seamless steel pipe with good fatigue resistance, si is a residual element of steel after smelting and deoxidizing. In the invention, the content of Si element in steel is reduced as much as possible, and the lower the content of Si element in steel is, the better the cold workability of the material is. Therefore, in the high-strength seamless steel pipe with good fatigue resistance, the mass percentage of Si is controlled to be less than or equal to 0.35 percent.
Of course, in some preferred embodiments, the mass percentage of Si element may be preferably controlled to Si.ltoreq.0.25% for better implementation.
Mn: in the high-strength seamless steel pipe with good fatigue resistance, the content of Mn element is improved to be beneficial to improving the strength of the material, and Mn element can effectively stabilize impurity element P, S, avoid the formation of low-melting-point sulfide and improve the hot processing performance of the material. The content of Mn element in the steel is not too low, and when the content of Mn element in the steel is low, P, S element cannot be well stabilized, and the required effect cannot be achieved. In addition, it should be noted that the content of Mn element in the steel is not too high, and too high content of Mn element in the steel may cause severe cold working deformation hardening, and aggravate die wear. Based on the above, in the high-strength seamless steel pipe with good fatigue resistance, the mass percentage of Mn is controlled to be between 0.5 and 1.0%.
Of course, in some preferred embodiments, the mass percentage of Mn may be preferably controlled to be between 0.55 and 0.95% for better implementation.
Cr: in the high-strength seamless steel pipe with good fatigue resistance, the content of Cr element is improved, so that the hardenability of the material is improved, the strength and fatigue resistance of the material are improved, and the strength and toughness of the material are ensured by matching with the content of C and Mo. Therefore, in the high-strength seamless steel pipe with good fatigue resistance, the mass percentage of Cr is controlled to be between 0.6 and 1.6 percent.
Of course, in some preferred embodiments, the mass percentage of Cr may be preferably controlled to be between 0.80 and 1.20% for better implementation.
Mo: in the high-strength seamless steel pipe with good fatigue resistance, the Mo element has a solidification strengthening effect, so that the strength and tempering stability of the steel can be improved, and the strength and toughness of the material can be ensured by matching the Mo element with the C element, so that the anti-torsional fatigue capability of the material is improved. Therefore, in the high-strength seamless steel pipe with good fatigue resistance, the mass percentage content of Mo is controlled to be between 0.1 and 0.35 percent. Of course, in some preferred embodiments, in order to obtain a more preferable implementation effect, the mass percentage of Mo may be preferably controlled to be between 0.15 and 0.30%.
N: in the high-strength seamless steel pipe with good fatigue resistance, the N element can effectively improve the strength and low-temperature toughness of the steel, but the content of the N element in the steel is not too high, and when the content of the N element in the steel is too high, N compound inclusion is easy to form. Therefore, in the high-strength seamless steel pipe with good fatigue resistance, the mass percentage of N is controlled to be between 0.0035 and 0.0085 percent.
Of course, in certain preferred embodiments, the mass percent of N may be preferably controlled between 0.0045 and 0.0065% for better performance.
Al, ca: in the high-strength seamless steel pipe with excellent fatigue resistance, both the Al element and the Ca element are elements added to the steel for deoxidization. In the invention, si is the residual element of steel after smelting and deoxidizing, in order to ensure that the steel only contains lower Si content, the O removal mode in the molten steel smelting process needs to be changed, so that the deoxidizing level needs to be ensured by comprehensively controlling the content of Al and Ca, and the corresponding nonmetallic inclusion has no adverse effect on the fatigue resistance. Based on the above, in the high-strength seamless steel pipe with excellent fatigue resistance, the content of Al element is controlled to be 0.020-0.055% by mass, and the content of Ca element is controlled to be 0.0005-0.005% by mass.
Of course, in some preferred embodiments, to obtain a more preferable implementation effect, the mass percentage of Al may be preferably controlled to be between 0.025 and 0.045%, and the mass percentage of Ca may be controlled to be between 0.001 and 0.004%.
Further, in the high-strength seamless steel pipe with good fatigue resistance, the mass percentage of each chemical element satisfies at least one of the following:
C：0.31～0.36％，
Si≤0.25％，
Mn：0.55～0.95％，
Cr：0.80～1.20％，
Mo：0.15～0.30％，
N：0.0045～0.0065％,
Al：0.025～0.045％,
Ca：0.001～0.004％。
further, in the high-strength seamless steel pipe with good fatigue resistance, among unavoidable impurities, P is less than or equal to 0.015%, S is less than or equal to 0.008%, and O is less than or equal to 0.0035%.
In the above technical solution, P, S and O are both unavoidable impurity elements in steel, and in order to obtain a steel product with better performance and better quality, the content of impurity elements in steel should be reduced as much as possible under the condition of allowable technical conditions. In the invention, P, S element in steel is iron and steel raw and auxiliary materials or impurity elements introduced in the production process, P element can embrittle crystal boundary to degrade toughness and processability of the material, S element can form sulfide with low melting point to degrade the processability of the material and mechanical properties of the material.
Further, in the high-strength seamless steel pipe with good fatigue resistance, the microstructure is ferrite and sorbite.
Further, in the high-strength seamless steel pipe excellent in fatigue resistance according to the present invention, the half decarburization depth from the outer wall surface to the inside is 120 μm or less in the wall thickness direction.
Further, in the high-strength seamless steel pipe having excellent fatigue resistance according to the present invention, the diameter is 30 to 55mm and/or the wall thickness is 3.0 to 5.5mm.
Further, in the high-strength seamless steel pipe with good fatigue resistance, the performance before tempering heat treatment of the high-strength seamless steel pipe meets the following conditions: yield strength rp0.2:300-450MPa, tensile strength Rm is more than or equal to 450MPa, and elongation A 50 ≥22％。
Further, in the high-strength seamless steel pipe with good fatigue resistance, the performance after tempering heat treatment of the high-strength seamless steel pipe meets at least one of the following: yield strength Rp0.2 is more than or equal to 1200MPa, tensile strength Rm is more than or equal to 1700MPa, and elongation A 50 More than or equal to 8 percent, the fatigue life under high input torque is more than or equal to 3000 times, the fatigue life under medium input torque is more than or equal to 30000 times, and the fatigue life under low input torque is more than or equal to 1000000 times.
Accordingly, another object of the present invention is to provide a method for manufacturing a high-strength seamless steel pipe with good fatigue resistance, which is simple to produce, and the obtained high-strength seamless steel pipe has good room temperature mechanical properties, cold workability, and good torsion fatigue resistance life, and also has excellent toughness, no cracks in cold working, no cracks in quenching and tempering, and is particularly suitable for parts bearing high torsion load, such as automobile driving shafts, and has good popularization prospect and application value.
In order to achieve the above object, the present invention provides a method for manufacturing the high-strength seamless steel pipe having excellent fatigue resistance, comprising the steps of:
(1) Preparing a tube blank;
(2) Heating, perforating, hot rolling and sizing to obtain a hot rolled pipe;
(3) Intermediate heat treatment;
(4) Cold drawing or cold rolling;
(5) Normalizing or annealing heat treatment.
In the above technical solution of the present invention, in order to ensure that the high-strength seamless steel pipe manufactured by the above manufacturing method has excellent performance, the requirements of the present automobile drive shaft on the dimensional accuracy of the pipe and the surface state in the cold die forging process are met, after the hot rolled pipe is obtained in the above step (2), the obtained hot rolled pipe may be further subjected to intermediate heat treatment, pickling lubrication, cold drawing or cold rolling to the required specification and dimensional accuracy, and further normalizing or annealing heat treatment.
Further, in the production method of the present invention, in the step (2), the heating temperature is 1180 to 1300 ℃, and then the heat is preserved for 2 to 6 hours.
Further, in the production method of the present invention, in the step (2), the perforation temperature is 950 to 1250 ℃.
In the technical scheme, in the step (2) of the manufacturing method, the pipe blank is controlled to be heated and kept at 1180-1300 ℃ for 2-6 hours, so that the pipe blank can be effectively ensured to have good thermoplasticity. Correspondingly, high-temperature deformation such as hot rolling and sizing is controlled to be carried out at a temperature of between 950 and 1250 ℃, which is beneficial to control the generation of deformation defects.
Further, in the production method of the present invention, in the step (3), annealing is performed at a temperature range of 680 to 900 ℃ and the temperature is kept for 0.25 to 3 hours.
In the technical scheme, the hot rolled pipe needs to be subjected to intermediate heat treatment in the step (3), is annealed at the temperature of 680-900 ℃ and is kept for 0.25-3 hours. This operation is to ensure that the cold drawing or cold rolling process of the subsequent step (4) proceeds smoothly.
Further, in the manufacturing method of the present invention, in the step (5), the normalizing or annealing temperature is 700 to 880 ℃, the holding time is 0.5 to 3 hours, and then air cooling or air cooling is performed.
In the technical scheme, the cold drawn or cold rolled pipe material is normalized or annealed at the temperature of 700-880 ℃, the heat preservation is carried out for 0.5-3 hours, and the atmosphere of an annealing furnace is controlled, so that the manufactured high-strength seamless steel pipe is ensured to be free from full decarburization, the half decarburization depth is less than or equal to 120 mu m, ferrite+sorbite tissues are ensured to be obtained through the coordination of the normalizing temperature and the cooling mode, and the high-strength seamless steel pipe with the strength and the toughness meeting the requirements of cold die forging processing is ensured to be obtained.
Further, in the manufacturing method of the invention, the method further comprises the step of (6) quenching and tempering heat treatment, wherein the quenching temperature is 880-920 ℃, the heat preservation time is 0.5-2 min, and then water cooling is carried out; tempering temperature is 150-300 ℃, heat preservation time is 20-40 min, and then air cooling is carried out.
Compared with the prior art, the high-strength seamless steel pipe with good fatigue resistance and the manufacturing method thereof have the following advantages:
according to the invention, the high-strength seamless steel pipe with good fatigue resistance can be obtained by reasonably optimizing and designing chemical components and matching with a manufacturing process, and the high-strength seamless steel pipe not only has good room temperature mechanical property and cold processing property, but also has good torsion fatigue resistance life.
The performance before quenching and tempering heat treatment of the high-strength seamless steel pipe with good fatigue resistance produced by the invention meets the following conditions: yield strength rp0.2:300-450MPa, tensile strength Rm is more than or equal to 450MPa, and elongationA 50 More than or equal to 22 percent; the performance after tempering heat treatment meets the following conditions: yield strength Rp0.2 is more than or equal to 1200MPa, tensile strength Rm is more than or equal to 1700MPa, and elongation A 50 More than or equal to 8 percent, the fatigue life under high input torque (input torque 2000 N.m) is more than or equal to 3000 times, the fatigue life under medium input torque (input torque 1200 N.m) is more than or equal to 30000 times, and the fatigue life under low input torque (input torque 800 N.m) is more than or equal to 1000000 times. The high-strength seamless steel pipe has no cracks in the cold working process, has no cracks in the quenching and tempering process, is particularly suitable for parts bearing high-strength torsional load such as automobile driving shafts and the like, and has very wide application prospect.
Drawings
Fig. 1 schematically shows the hardenability test curves of the high-strength seamless steel pipes of example 7 and example 8, which were measured by heat-preserving at 900 ℃ for 40 min.
Fig. 2 is a photograph of the microstructure morphology of the high strength seamless steel pipe of example 9 at one viewing angle.
Fig. 3 is a photograph of the microstructure morphology of the high strength seamless steel pipe of example 9 at another viewing angle.
Detailed Description
The high-strength seamless steel pipe with excellent fatigue resistance and the manufacturing method thereof according to the present invention will be further explained and illustrated with reference to specific examples and drawings, but the explanation and illustration do not unduly limit the technical scheme of the present invention.
Examples 1 to 15 and comparative examples 1 to 5
The high strength seamless steel pipes of examples 1 to 15 having good fatigue resistance and the comparative seamless steel pipes of comparative examples 1 to 5 were each produced by the following steps:
(1) According to the chemical compositions shown in the following table 1, smelting and refining casting are performed by using an electric furnace or a converter to obtain a tube blank, and then continuous casting and cutting are performed to obtain the tube blank with the required size.
(2) Heating, perforating, hot rolling and sizing to obtain a hot rolled pipe: the pipe blank is heated and kept at 1180-1300 ℃ for 2-6 hours, then high Wen Chuankong is carried out between 950-1250 ℃, high temperature deformation such as hot rolling and sizing is carried out, and the like, thus the hot rolled pipe with phi of 52-76 mm multiplied by 4.5-8.5 mm is processed.
(3) Intermediate heat treatment: the hot rolled pipe is controlled to anneal at 680-900 ℃ and kept for 0.25-3 h.
(4) Cold drawing or cold rolling.
(5) Normalizing or annealing heat treatment: the normalizing or annealing temperature is controlled to be 700-880 ℃, the heat preservation time is controlled to be 0.5-3 h, and then air cooling or air cooling is performed. The diameter phi of the finished seamless steel pipe is between 30 and 55mm, and the wall thickness is 3.0 to 5.5mm.
In the present invention, the chemical composition design and the related process of the high-strength seamless steel pipes with good fatigue resistance in examples 1 to 15 all meet the design specification requirements of the present invention. Whereas the comparative seamless steel pipes of comparative examples 1 to 5 had parameters in the chemical composition design that did not meet the requirements of the design specifications of the present invention.
Table 1 shows the mass percentages of each chemical element of the high-strength seamless steel pipes of examples 1 to 15, which have excellent fatigue resistance, and the comparative seamless steel pipes of comparative examples 1 to 5.
Table 1. (wt.%) Fe and unavoidable impurities other than P, S and O in balance
Table 2 shows specific process parameters of the high strength seamless steel pipes of examples 1 to 15 having good fatigue resistance and the comparative seamless steel pipes of comparative examples 1 to 5 in the above process steps.
Table 2.
The obtained high-strength seamless steel pipes with good fatigue resistance of examples 1 to 15 and comparative seamless steel pipes of comparative examples 1 to 5 were sampled respectively, and room temperature mechanical property detection and cold workability detection were performed respectively on the finished plates of each example and comparative example. The results of the mechanical property test and the cold workability test of each of the examples and comparative examples are shown in Table 3, respectively.
The relevant performance test means are as follows:
mechanical property test: part 1 of the tensile test of metallic materials according to GB/T228.1-2010: the room temperature tensile test method is used for detecting the mechanical properties of the seamless steel pipes of each embodiment and the comparative example.
Cold workability detection: the seamless steel pipes of each of the examples and comparative examples were subjected to die forging, and a cold swaging apparatus for a practical driveshaft tube. After the die forging process is completed, it is necessary to detect whether or not the seamless steel pipes of each of the examples and comparative examples have cracks in the die forging process.
Table 3 shows the results of the room temperature mechanical property test of the high strength seamless steel pipes of examples 1 to 15 having good fatigue resistance and the comparative seamless steel pipes of comparative examples 1 to 5.
Table 3.
In table 3, "Σ" indicates: the seamless steel pipe of the example or the comparative example does not generate cracks in the die forging process; "X" indicates that the example or comparative example developed cracks in the swaging process.
After the mechanical property detection and cold workability detection of the seamless steel pipes of each example and comparative example are completed, quenching and tempering heat treatment is required to be carried out on the high-strength seamless steel pipes with good fatigue resistance of finished product examples 1-15 and the comparative seamless steel pipes of comparative examples 1-5, wherein the quenching temperature is 880-920 ℃, the heat preservation time is 0.5-2 min, and then water cooling is carried out; tempering temperature is 150-300 ℃, heat preservation time is 20-40 min, and then air cooling is carried out. The specific tempering heat treatment process parameters used for the seamless steel pipes of each example and comparative example are shown in table 4. Table 4 shows specific process parameters of the quenching and tempering heat treatment of the high-strength seamless steel pipes of examples 1 to 15 and the comparative seamless steel pipes of comparative examples 1 to 5, which have excellent fatigue resistance.
Table 4.
After the tempering heat treatment, the high-strength seamless steel pipes of examples 1 to 15 and comparative examples 1 to 5 after the tempering heat treatment were sampled again, respectively, and the normal-temperature mechanical properties and the torsional fatigue properties after the tempering were detected, and the test results of the tempering heat treatment of each example and comparative example are shown in table 5, respectively.
The method for detecting the normal-temperature mechanical properties of the seamless steel pipes of each example and the comparative example after the tempering heat treatment is the same as the mechanical property detection means adopted before the tempering heat treatment.
The relevant torsion fatigue performance test means are as follows:
torsional fatigue performance test: the fatigue life of the parts of the seamless steel pipes of each example and comparative example was tested by using a torsion fatigue tester dedicated to the transmission shaft under the high load condition with an input torque of 2000n.m, the medium load condition with an input torque of 1200n.m, and the low load condition with an input torque of 800n.m, and the torsion fatigue performance was measured.
Table 5 shows test results of the high-strength seamless steel pipes having excellent fatigue resistance of examples 1 to 15 after heat treatment by tempering and the comparative seamless steel pipes of comparative examples 1 to 5.
Table 5.
As can be seen from the combination of tables 3 and 5, the high strength seamless steel pipes of examples 1 to 15 were significantly superior in their comprehensive mechanical properties to the comparative seamless steel pipes of comparative examples 1 to 3 before the tempering heat treatment. After tempering heat treatment, the high-strength seamless steel pipes of the examples 1-15 are obviously superior to the comparative seamless steel pipes of the comparative examples 4-5 in comprehensive mechanical properties, and are superior to the comparative seamless steel pipes of the comparative examples 2 and 5 in torsional fatigue properties.
As can be seen from Table 3, the high-strength seamless steel pipes of examples 1 to 15 of the present invention, which had good fatigue resistance, had excellent room temperature mechanical properties and cold workability before the tempering heat treatment, had a yield strength Rp0.2 of 312MPa to 448MPa, a tensile strength Rm of 484 to 648MPa, and an elongation A 50 Between 22% and 31%.
Accordingly, as can be seen from table 5, the high-strength seamless steel pipes with good fatigue resistance of examples 1 to 15 according to the present invention still have very excellent room temperature mechanical properties after the tempering heat treatment, and in addition, they have good torsional fatigue resistance life. The high-strength seamless steel pipes of examples 1 to 15 produced by the invention have the following properties after quenching and tempering heat treatment: the yield strength Rp0.2 is 1213 MPa-1493 MPa, the tensile strength Rm is 1703 MPa-1892 MPa, and the elongation A is 50 Between 8% and 15%, the fatigue life at high input torque (input torque 2000 n.m) is between 3289 and 5148 times, the fatigue life at medium input torque (input torque 1200 n.m) is between 32908 and 59891 times, and the fatigue life at low input torque (input torque 800 n.m) is between 1062203 ～ 1574338 times.
From the above, it can be seen that the high-strength seamless steel pipe with good fatigue resistance has very excellent performance, and the high-strength seamless steel pipe not only has no crack in the cold working process, but also has no crack in the quenching and tempering process, and is particularly suitable for parts bearing high-strength torsion load, such as automobile driving shafts, and has very wide application prospect.
Fig. 1 schematically shows the hardenability test curves of the high-strength seamless steel pipes of example 7 and example 8, which were measured by heat-preserving at 900 ℃ for 40 min.
As shown in fig. 1, fig. 1 schematically shows the change curves of the hardness of the high-strength seamless steel pipes of example 7 and example 8 with distance, and from the change curves, it can be seen that the hardness after tempering can reach more than 55HRC within the specification wall thickness range of the product of the invention.
Fig. 2 is a photograph of the microstructure morphology of the high strength seamless steel pipe of example 9 at one viewing angle.
Fig. 3 is a photograph of the microstructure morphology of the high strength seamless steel pipe of example 9 at another viewing angle.
As can be seen from fig. 2 and 3, in the present embodiment, the microstructure of the high-strength seamless steel pipe of example 9 is ferrite+sorbite, and the half decarburization depth from the outer wall surface to the inside in the wall thickness direction is 120 μm or less.
It should be noted that the combination of the technical features in the present invention is not limited to the combination described in the claims or the combination described in the specific embodiments, and all the technical features described in the present invention may be freely combined or combined in any manner unless contradiction occurs between them.
It should also be noted that the above-recited embodiments are merely specific examples of the present invention. It is apparent that the present invention is not limited to the above embodiments, and similar changes or modifications will be apparent to those skilled in the art from the present disclosure, and it is intended to be within the scope of the present invention.
Claims (13)
1. A high-strength seamless steel pipe with good fatigue resistance is characterized by comprising the following chemical elements in percentage by mass in addition to Fe and unavoidable impurities:
C：0.28～0.38％，Si≤0.35％，Mn：0.5～1.0％，Cr：0.6～1.6％，Mo：0.1～0.35％，N：0.0035～0.0085％,Al：0.020～0.055％,Ca：0.0005～0.005％；
the microstructure is ferrite and sorbite; in the wall thickness direction, the half decarburization depth inwards from the outer wall surface is less than or equal to 120 mu m;
the performance of the heat-treated material after tempering heat treatment meets the following conditions: the fatigue life under high input torque is more than or equal to 3000 times, the fatigue life under medium input torque is more than or equal to 30000 times, and the fatigue life under low input torque is more than or equal to 1000000 times.
2. The high-strength seamless steel pipe with good fatigue resistance according to claim 1, wherein the mass percentage of each chemical element is as follows:
c: 0.28-0.38%, si is more than 0 and less than or equal to 0.35%, mn:0.5 to 1.0 percent, cr:0.6 to 1.6 percent, mo:0.1 to 0.35 percent, N:0.0035 to 0.0085 percent, al:0.020 to 0.055 percent, ca:0.0005 to 0.005 percent; the balance being Fe and unavoidable impurities.
3. The high-strength seamless steel pipe with excellent fatigue resistance according to claim 1 or 2, wherein the mass percentage of each chemical element satisfies at least one of the following:
C：0.31～0.36％，
Si≤0.25％，
Mn：0.55～0.95％，
Cr：0.80～1.20％，
Mo：0.15～0.30％，
N：0.0045～0.0065％,
Al：0.025～0.045％,
Ca：0.001～0.004％。
4. the high-strength seamless steel pipe having excellent fatigue resistance according to claim 1 or 2, wherein among the unavoidable impurities, P is 0.015% or less, S is 0.008% or less, and O is 0.0035% or less.
5. The high-strength seamless steel pipe having excellent fatigue resistance according to claim 1 or 2, wherein the diameter is 30 to 55mm and/or the wall thickness is 3.0 to 5.5mm.
6. The high-strength seamless steel pipe having excellent fatigue resistance according to claim 1 or 2, wherein the performance before heat treatment for tempering satisfies: yield strength Rp0.2 is 300-450MPa, tensile strength
Rm is more than or equal to 450MPa, and elongation A 50 ≥22％。
7. The high-strength seamless steel pipe having excellent fatigue resistance according to claim 1 or 2The method is characterized in that the performance after tempering heat treatment meets at least one of the following: yield strength Rp0.2 is more than or equal to 1200MPa, tensile strength Rm is more than or equal to 1700MPa, and elongation A 50 ≥8％。
8. The method for producing a high-strength seamless steel pipe having excellent fatigue resistance according to any one of claims 1 to 7, comprising the steps of:
(1) Preparing a tube blank;
(2) Heating, perforating, hot rolling and sizing to obtain a hot rolled pipe;
(3) Intermediate heat treatment;
(4) Cold drawing or cold rolling;
(5) Normalizing or annealing heat treatment.
9. The method according to claim 8, wherein in the step (2), the heating temperature is 1180 to 1300 ℃, followed by heat preservation for 2 to 6 hours.
10. The method according to claim 8, wherein in the step (2), the perforation temperature is 950 to 1250 ℃.
11. The method according to claim 8, wherein in the step (3), annealing is performed at a temperature ranging from 680 to 900 ℃ and the temperature is kept for 0.25 to 3 hours.
12. The method according to claim 8, wherein in the step (5), the normalizing or annealing temperature is 700 to 880 ℃, and the holding time is 0.5 to 3 hours.
13. The method according to any one of claims 8 to 12, further comprising the step of (6) quenching and tempering, wherein the quenching temperature is 880 to 920 ℃, the holding time is 0.5 to 2 minutes, and then water-cooling; tempering temperature is 150-300 ℃, heat preservation time is 20-40 min, and then air cooling is carried out.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11302785A (en) * | 1998-04-20 | 1999-11-02 | Sumitomo Metal Ind Ltd | Steel for seamless steel pipe |
| CN105154765A (en) * | 2015-09-24 | 2015-12-16 | 宝山钢铁股份有限公司 | Seamless steel tube with high strength and toughness and manufacturing method thereof |
| CN106133176A (en) * | 2014-04-03 | 2016-11-16 | 杰富意钢铁株式会社 | Pipe as fuel injection seamless steel pipe |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11302785A (en) * | 1998-04-20 | 1999-11-02 | Sumitomo Metal Ind Ltd | Steel for seamless steel pipe |
| CN106133176A (en) * | 2014-04-03 | 2016-11-16 | 杰富意钢铁株式会社 | Pipe as fuel injection seamless steel pipe |
| CN105154765A (en) * | 2015-09-24 | 2015-12-16 | 宝山钢铁股份有限公司 | Seamless steel tube with high strength and toughness and manufacturing method thereof |
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