CN117286395A - High-strength and high-toughness seamless steel tube for free-cutting motor shaft and manufacturing method thereof - Google Patents

High-strength and high-toughness seamless steel tube for free-cutting motor shaft and manufacturing method thereof Download PDF

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Publication number
CN117286395A
CN117286395A CN202210690205.1A CN202210690205A CN117286395A CN 117286395 A CN117286395 A CN 117286395A CN 202210690205 A CN202210690205 A CN 202210690205A CN 117286395 A CN117286395 A CN 117286395A
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strength
percent
motor shaft
seamless steel
cutting motor
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骆素珍
翟国丽
高展
刘文灏
刘慧芳
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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Priority to CN202210690205.1A priority Critical patent/CN117286395A/en
Priority to PCT/CN2023/100773 priority patent/WO2023241700A1/en
Publication of CN117286395A publication Critical patent/CN117286395A/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
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    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • 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
    • C21D1/26—Methods of annealing
    • C21D1/28—Normalising
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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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
    • C—CHEMISTRY; METALLURGY
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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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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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—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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    • 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
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • 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

Abstract

The invention discloses a high-strength and high-toughness seamless steel tube for a free-cutting motor shaft, which contains Fe and unavoidable impurity elements and also contains the following chemical elements in percentage by mass: c: 0.32-0.48%, si is more than 0 and less than or equal to 0.20%, mn:0.5 to 1.2 percent, S:0.02 to 0.10 percent, cr:0.6 to 1.5 percent, mo:0.15 to 0.35 percent, cu is less than or equal to 0.25 percent, ni is less than or equal to 0.25 percent, ce+La is less than or equal to 0.015 percent, al:0.015 to 0.045 percent, ca+Mg:0.001 to 0.006 percent. Correspondingly, the invention also discloses a manufacturing method of the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, which comprises the following steps: (1) preparing a tube blank; (2) heating, perforating, hot rolling and reducing; (3) intermediate heat treatment: annealing the hot rolled pipe material at the temperature of 750-880 ℃ for 30-80 min; (4) cold drawing; (5) heat treatment of finished products: normalizing at 800-880 deg.c for 30-60 min to obtain ferrite-pearlite structure.

Description

High-strength and high-toughness seamless steel tube for free-cutting motor shaft and manufacturing method thereof
Technical Field
The present invention relates to a steel pipe and a method for manufacturing the same, and more particularly, to a seamless steel pipe and a method for manufacturing the same.
Background
In recent years, under the large background of carbon reduction and pollution reduction, the sales volume of new energy automobiles starts to advance suddenly, the new energy automobiles themselves are light and have more and more severe emission reduction requirements, in order to achieve the maximum light and high-strength materials such as high-strength steel, magnesium aluminum alloy, carbon brazing and the like are adopted as main automobile bodies, parts which occupy smaller weight in the whole automobile bodies such as motor shafts and the like are also included in weight reduction rows, and hollow pipes are increasingly used for replacing solid bars and forging materials.
As is well known, components such as the motor shaft of an automobile, which are very important safety components, perform the function of transmitting motor torque to the drive wheels. Because the motor shaft runs at high speed and bears great torsion moment, vibration impact force and other complex loads, the material is required to have high toughness so as to ensure the high-speed stable running and enough torsion resistance and fatigue resistance of the motor shaft.
However, in the current prior art, because of different vehicle types and the like, different motor shafts can meet the service performance requirements through the processing procedures of integral cold rotary forging, cold extrusion, cutting processing and the like. Therefore, the material design of the motor shaft must be compatible with high strength and toughness, high fatigue performance and good cold workability.
For example: the invention discloses a high-strength steel, which is disclosed in Chinese patent literature with publication number of CN104962838A and publication date of 2015, 10 months and 7 days, namely a high-strength steel, high-strength plastic seamless steel tube for automobile transmission half shafts and a manufacturing method thereof, and comprises the following 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%; al:0.015 to 0.060; nb 0.02-0.1%; v:0.02-0.15%. In the technical scheme, the low-C design is adopted, the strength of the steel pipe is low, the welding is facilitated, and the automobile half shaft is more suitable for friction stir welding production.
Also for example: chinese patent document publication No. CN1388834a, publication No. 1 month and 1 day 2003, entitled "high carbon steel pipe excellent in cold workability and high frequency hardening properties and method for producing the same", discloses a high carbon steel pipe and method for producing the same, comprising the following chemical components by mass percent: c:0.30 to 0.80 percent, si is less than or equal to 2 percent, mn is less than or equal to 3 percent. In the technical scheme, a special rolling technology is utilized to obtain a structure with cementite less than 1um, so that the cold processing performance and the high-frequency hardening performance are improved.
Unlike the above prior art, in order to solve the problems existing in the prior art, the present invention is expected to develop and obtain a new seamless steel pipe for high-strength and high-toughness free-cutting motor shafts and a method for manufacturing the same.
Disclosure of Invention
The invention aims to provide a seamless steel tube for a high-strength and high-toughness free-cutting motor shaft, which can obtain very excellent processing performance through reasonable component matching and process design, has excellent mechanical properties before and after tempering heat treatment, has better plastic toughness, is particularly suitable for preparing motor shaft parts bearing high torsional load, and has good popularization prospect and application value.
In order to achieve the above object, the present invention provides a seamless steel tube for a high-strength and high-toughness free-cutting motor shaft, which contains Fe and unavoidable impurity elements, and further contains the following chemical elements in percentage by mass:
C：0.32～0.48％，0＜Si≤0.20％，Mn：0.5～1.2％，S：0.02-0.10％，Cr：0.6～1.5％，Mo：0.15～0.35％，Cu≤0.25％，Ni≤0.25％，Ce+La≤0.015％，Al：0.015～0.045％，Ca+Mg：0.001～0.006％。
further, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentages of the chemical elements are as follows:
c: 0.32-0.48%, si is more than 0 and less than or equal to 0.20%, mn:0.5 to 1.2 percent, S:0.02-0.10%, cr:0.6 to 1.5 percent, mo:0.15 to 0.35 percent, cu is less than or equal to 0.25 percent, ni is less than or equal to 0.25 percent, ce+La is less than or equal to 0.015 percent, al:0.015 to 0.045 percent, ca+Mg: 0.001-0.006%, and the balance of Fe and unavoidable impurities.
In the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the design principle of each chemical element is as follows:
c: in the seamless steel tube for the high-toughness free-cutting motor shaft, the improvement of the content of the element C is beneficial to improving the strength and fatigue resistance of the material, but the content of the element C in the steel tube is not too high, and when the content of the element C is too high, the toughness and plasticity of the material are reduced, cold working is not facilitated, and the quality problems of easiness in processing cracks, serious decarburization and the like are caused. Therefore, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentage of the C element is controlled to be between 0.32 and 0.48 percent, so that the quenching hardness and the hardenability of the material can be ensured, the hardenability of the material is ensured, the quenching crack sensitivity is reduced, and the cold processing performance of the steel is ensured.
Of course, in some preferred embodiments, in order to obtain a better implementation effect, the mass percentage of the element C may be further preferably controlled between 0.38 and 0.45%.
Si: in the seamless steel tube for the high-toughness free-cutting motor shaft, si element has larger influence on cold workability, the lower the content of the Si element in the steel tube is, the better the cold workability of the steel tube is, in general, si is the residual element of the steel after smelting and deoxidizing, and if the lower content of Si is required, the deoiling mode in the smelting process of molten steel 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 is ensured to have no adverse influence on the fatigue resistance. Therefore, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentage of Si element is controlled to be more than 0 and less than or equal to 0.20 percent.
Of course, in some preferred embodiments, in order to obtain a more preferable implementation effect, the mass percentage of Si element may be further preferably controlled to be 0 < Si.ltoreq.0.15%.
Mn: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the content of Mn element is improved, the strength of the material can be improved, mn element P, S can be stabilized, the formation of low-melting-point sulfide is avoided, and the hot processing performance of the material is improved. In order to achieve the above effect, the content of Mn element in the steel is not too low, and when the content of Mn element in the steel is too low, P, S element cannot be well stabilized; meanwhile, the content of Mn element in the steel is not too high, and when the content of Mn element in the steel is too high, cold working deformation hardening is serious, so that die abrasion is increased. Therefore, considering the influence of Mn element content on the performance of steel, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentage of Mn element is controlled to be between 0.5 and 1.2 percent.
Of course, in some preferred embodiments, in order to obtain a more preferable implementation effect, the mass percentage of Mn element may be further preferably controlled to be between 0.6 and 0.9%.
S: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, S is not an impurity element introduced in the steel raw and auxiliary materials or the production process, but is a sulfide forming element which is particularly added after the deoxidation and desulfurization process in the smelting process so as to promote the formation of dispersed manganese sulfide in the steel, thereby endowing the material with good cutting processing performance. However, it should be noted that the content of S element in the steel is not too high, and when the content of S element in the steel is too high, aggregation of sulfides is easily caused, so that the mechanical property and fatigue property of the material can be deteriorated. Therefore, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentage of the S element is controlled to be between 0.02 and 0.10 percent.
Of course, in some preferred embodiments, in order to obtain a better implementation effect, the mass percentage of the S element may be further preferably controlled to be between 0.04 and 0.06%.
Cr, mo: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the improvement of Cr and Mo contents can improve the hardenability of a material and improve the strength and fatigue resistance of the material, and the seamless steel tube can be matched with the C and Mo contents so as to ensure the strength and toughness of the material. However, it should be noted that the mass percentages of Cr and Mo elements in the steel are not too high, which greatly increases the alloy cost. Therefore, in order to exert the beneficial effects of Cr and Mo, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percent of the Cr element is controlled to be between 0.6 and 1.5 percent, and the mass percent of the Mo element is controlled to be between 0.15 and 0.35 percent.
Of course, in some preferred embodiments, in order to obtain a more preferable implementation effect, the mass percentage of Cr element may be further preferably controlled to be between 0.8 and 1.2%.
Cu: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, cu element is matched with a proper amount of Cr, ni and other elements, so that the material can be endowed with certain atmospheric corrosion resistance, but the problem of thermal brittleness in the hot working process is caused by too high Cu element. Therefore, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentage of Cu element is controlled to be less than or equal to 0.25 percent.
Of course, in some preferred embodiments, in order to obtain a more preferable implementation effect, the mass percentage of Cu element may be further preferably controlled to be between 0.1 and 0.25%.
Ni: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the Ni element and the Cu element are matched to endow a material with certain atmospheric corrosion resistance, and meanwhile, the problem of thermal embrittlement caused by Cu is improved, but when Ni in the steel is too high, the cost is obviously increased. Therefore, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentage of Ni element is required to be controlled to be less than or equal to 0.25%.
Of course, in some preferred embodiments, in order to obtain a more preferable implementation effect, the mass percentage of the Ni element may be further preferably controlled to be between 0.1 and 0.25%.
Ce. La: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, ce and La are rare earth elements, which can play a role in refining grains, and the rare earth elements Ce and La can be matched with Cu and Ni elements, so that the atmospheric corrosion resistance of the material is improved. However, rare earth elements Ce and La are also active, and when the addition amount of the rare earth elements Ce and La in steel is too high, smelting and continuous casting are difficult. Therefore, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the sum of the mass percentages of Ce and La elements is controlled to be less than or equal to 0.015 percent.
Of course, in some preferred embodiments, in order to obtain a better implementation effect, the sum of the mass percentages of Ce and La elements, ce+la, may be further preferably controlled to be between 0.001 and 0.01%.
Al: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, al is a deoxidizer in the smelting process, and can ensure the deoxidizing effect of steel types together with elements such as Si and the like, and ensure the purity of the steel, thereby ensuring the fatigue resistance of the material. However, it should be noted that the content of Al element in the steel is not too high, and when the content of Al element in the steel is too high, abnormal alumina inclusion may be caused. Therefore, in order to exert the beneficial effects of the Al element, the mass percentage of the Al element is controlled to be between 0.015 and 0.045 percent in the invention.
Of course, in some preferred embodiments, in order to obtain a more preferable implementation effect, the content of the Al element by mass may be further preferably controlled to be between 0.015 and 0.035%.
Ca. Mg: in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, proper amounts of Ca and Mg can improve the shape and the performance of nonmetallic inclusion, thereby improving the fatigue performance of materials and the like. Therefore, in the seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to the present invention, in order to exert the beneficial effects of the Ca and Mg elements, the inventors can consider that Ca and/or Mg elements are added to the steel and the sum of the mass percentages of the Ca and Mg elements, ca+mg, is controlled to be 0.001 to 0.006%.
Of course, in some preferred embodiments, in order to obtain a better implementation effect, the sum of the mass percentages of the Ca and Mg elements, ca+Mg, may be further preferably controlled to be between 0.001 and 0.004%.
Furthermore, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, among unavoidable impurities, P is less than or equal to 0.015 percent, and O is less than or equal to 0.0030 percent.
Further, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, among unavoidable impurities, P is less than or equal to 0.015 percent and O is less than or equal to 0.0020 percent.
In the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the P element and the O element are both impurity elements in the steel tube, are impurity elements introduced into raw and auxiliary materials of steel or in the production process, and the content of the impurity elements in the seamless steel tube is reduced as far as possible in order to obtain the tube with better performance and better quality under the condition of technical conditions. Therefore, the content of P, O element in steel must be strictly controlled to P.ltoreq.0.015%, and O.ltoreq.0.0030%. Of course, in some preferred embodiments, in order to obtain a better implementation effect, the content of the P, O element may be further controlled to satisfy: p is less than or equal to 0.015 percent, and O is less than or equal to 0.0020 percent.
Further, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the mass percentage of each chemical element further satisfies at least one of the following:
C：0.38～0.45％，
0＜Si≤0.15％，
Mn：0.6～0.9％，
S：0.04～0.06％，
Cr：0.8～1.2％，
Cu：0.1～0.25％，
Ni：0.1～0.25％，
Al：0.015～0.035％，
Ce+La：0.001～0.01％，
Ca+Mg：0.001～0.004％。
further, in the seamless steel tube for a high-strength and high-toughness free-cutting motor shaft, the microstructure is ferrite and pearlite.
Further, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the microstructure subjected to quenching and tempering heat treatment is martensite and retained austenite with the volume phase ratio of less than or equal to 20%.
Further, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the yield strength is 420-540 MPa, the tensile strength is 550-680 MPa, and the elongation is more than or equal to 20%.
Further, in the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft, the performance of the seamless steel tube after quenching and tempering heat treatment meets the following conditions: yield strength Rp 0.2 Not less than 960MPa, tensile strength R m 1260MPa or more, elongation A 50 More than or equal to 8 percent, the hardness is more than or equal to 55HRC, the product of strength and elongation is more than 12000MPa, and the torsion resistance is more than or equal to 500KN.
Accordingly, another object of the present invention is to provide a method for manufacturing the seamless steel tube for a high-toughness free-cutting motor shaft, wherein the manufacturing method is designed optimally, the manufacturing process is simple and easy to implement, the seamless steel tube for a high-toughness free-cutting motor shaft can be effectively manufactured, and the method has a very good application prospect.
In order to achieve the above object, the present invention provides a method for manufacturing the seamless steel tube for a high-strength and high-toughness free-cutting motor shaft, comprising the steps of:
(1) Preparing a tube blank;
(2) Heating, perforating, hot rolling and reducing;
(3) Intermediate heat treatment: annealing the hot rolled pipe material at the temperature of 750-880 ℃ for 30-80 min;
(4) Cold drawing;
(5) And (3) heat treatment of a finished product: normalizing at 800-880 deg.c for 30-60 min to obtain ferrite-pearlite structure.
In the technical scheme of the invention, in the tube blank manufacturing process of the step (1), operators can smelt and refine the tube blank by using an electric furnace or a converter to pour the tube blank, and cut the tube blank to obtain the tube blank with the required size by using continuous casting.
In addition, in the step (3), during the intermediate heat treatment, the hot rolled tube stock is controlled to be annealed at a temperature of 750-880 ℃ and kept for 30-80 min, so that the cold rolling process of the subsequent step (4) can be ensured to be smoothly carried out.
In addition, in the heat treatment of the finished product in the step (5), the cold drawn pipe material prepared in the step (4) is required to be normalized at the temperature of 800-880 ℃, the heat preservation is carried out for 30-60 min, the atmosphere in the furnace is controlled, no full decarburization (namely no full ferrite tissue area on the surface of the steel pipe) is ensured, and the half decarburization depth is less than or equal to 150 mu m. In the technical scheme, the normalizing temperature and the cooling mode are controlled to be matched, so that the steel pipe can be ensured to obtain a ferrite and pearlite structure, and the normalized pipe with strength and toughness meeting the cold working requirements is obtained.
Further, in the production method of the present invention, in the step (2), the tube blank is heated and kept at 1220 to 1280 ℃ for 60 to 150 minutes.
Further, in the manufacturing method according to the present invention, in the step (2), the perforation temperature is controlled to 1150 to 1250 ℃.
Further, in the manufacturing method of the present invention, in the step (2), the hot continuous rolling temperature is controlled to be 1000 to 1200 ℃.
Further, in the manufacturing method of the present invention, in the step (2), the tension-reducing temperature is controlled to 900 to 1000 ℃.
Compared with the prior art, the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft and the manufacturing method thereof have the following advantages and beneficial effects:
in the invention, the inventor can obtain a brand-new seamless steel tube for the high-strength and high-toughness free-cutting motor shaft through reasonable component matching and process design, and the seamless steel tube not only has very excellent processing performance, but also has excellent mechanical properties before and after tempering heat treatment and has better plastic toughness.
The structure of the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft after the final product normalizing heat treatment is ferrite and pearlite, and the structure after further quenching and tempering heat treatment is martensite and residual austenite with the volume phase ratio of less than or equal to 20 percent.
The seamless steel tube for the high-strength and high-toughness free-cutting motor shaft has good room temperature mechanical property, cold processing property and good torsion resistance, the yield strength of the finished product is 420-540 MPa, the tensile strength is 550-680 MPa, and the elongation is more than or equal to 20%; the hardness after heat treatment reaches more than 55HRC, the product of the strength and the plastic product (the product of the tensile strength and the uniform elongation) is more than 12000MPa, the product can resist the torque of more than 500KN, and the yield strength R after heat treatment p0.2 Not less than 960MPa, tensile strength R m 1260MPa or more, elongation A 50 More than or equal to 8 percent, is particularly suitable for preparing motor shaft parts bearing high torsional load, and has good popularization prospect and application value.
Drawings
Fig. 1 is a photograph showing a metallographic structure of a seamless steel tube for a high-strength and high-toughness free-cutting motor shaft of example 1 after heat treatment.
Detailed Description
The high-strength and high-toughness seamless steel tube for a free-cutting motor shaft and the manufacturing method thereof according to the present invention will be further explained and illustrated with reference to the drawings and specific examples, but the explanation and illustration do not unduly limit the technical scheme of the present invention.
Examples 1 to 10 and comparative examples 1 to 2
The seamless steel tube for the high-strength and high-toughness free-cutting motor shaft and the comparative steel tube for the comparative examples 1-2 are prepared by the following steps:
(1) Smelting and refining by an electric furnace or a converter according to the mass percentages of chemical elements shown in the table 1 to obtain a tube blank, and continuously casting and cutting the tube blank to obtain the tube blank with the required size.
(2) Heating, perforating, hot rolling and reducing: heating and preserving the heat of the tube blank at 1220-1280 ℃ for 60-150 min, carrying out high Wen Chuankong at 1150-1250 ℃, carrying out hot continuous rolling at 1000-1200 ℃, further carrying out stretch reduction after the hot continuous rolling is finished, and controlling the stretch reduction temperature to 900-1000 ℃.
(3) Intermediate heat treatment: annealing the hot rolled pipe material at the temperature of 750-880 ℃ for 30-80 min.
(4) Cold drawing: after the intermediate heat treatment is completed, the steel is further cold drawn to the required specification and dimensional accuracy.
(5) And (3) heat treatment of a finished product: normalizing at 800-880 deg.c for 30-60 min to obtain ferrite-pearlite structure.
The chemical element components and the related process design of the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft in the embodiments 1 to 10 of the present invention all meet the requirements of the design specification of the present invention. The comparative steel pipes of comparative examples 1-2 were also prepared by the above-described process steps, but the chemical element compositions and/or the related process parameters thereof had parameters which did not meet the design of the present invention.
Table 1 shows the mass percentages of each chemical element in the seamless steel pipes for high-strength and high-toughness free-cutting motor shafts of examples 1 to 10 and the comparative steel pipes of comparative examples 1 to 2.
Table 1 (balance Fe and unavoidable impurities other than P, O)
Table 2 shows the specific process parameters employed in the above manufacturing process steps for the seamless steel pipes for high strength and toughness free-cutting motor shafts of examples 1-10 and comparative steel pipes of comparative examples 1-2.
Table 2.
The prepared seamless steel pipes for high-strength and high-toughness free-cutting motor shafts of the finished products of examples 1 to 10 and the comparative steel pipes of comparative examples 1 to 2 were sampled respectively, and each performance of the steel pipes of each example and comparative example before heat treatment by tempering was tested to obtain normal-temperature mechanical properties before tempering, and the test results of the related mechanical properties are shown in table 3.
The correlation performance detection means are as follows:
tensile test: according to section 1 of the tensile test according to GB/T228.1-2010 metallic materials: room temperature tensile test method to test yield strength, tensile strength and elongation values at room temperature of the steel pipes of each example and comparative example obtained before the tempering heat treatment.
Table 3 shows the results of performance tests of the seamless steel pipes for high-strength and high-toughness free-cutting motor shafts of examples 1 to 10 and the comparative steel pipes of comparative examples 1 to 2 before the quenching and tempering heat treatment.
Table 3.
As can be seen from the above Table 3, examples 1 to 10 have excellent mechanical properties, the yield strength Rp0.2 is 434-528MPa, and the tensile strength R m Between 572 and 662MPa, the elongation A 50 Between 21-34%.
Correspondingly, in order to further illustrate that the seamless steel tube for the high-strength and high-toughness free-cutting motor shaft still has very excellent performance after quenching and tempering heat treatment, the inventor further samples the prepared seamless steel tubes for the high-strength and high-toughness free-cutting motor shaft of finished product examples 1-10 and the comparative steel tubes of comparative examples 1-2 respectively, and carries out quenching and tempering heat treatment on the steel tubes of each example and comparative example, wherein the quenching and tempering heat treatment is carried out by controlling the quenching and tempering heat treatment, 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.
After finishing the tempering heat treatment for the sample steel pipes of examples and comparative examples, the inventors further conducted mechanical property tests on the steel pipes after the tempering heat treatment to measure the properties of the steel pipes after the tempering heat treatment, and the results of the related mechanical property tests are shown in table 4 below.
When the mechanical properties of the steel pipes of examples 1 to 10 and comparative examples 1 to 2 after the heat treatment for tempering were tested, the tensile test procedure was the same as that of the test procedure of Table 3, and the yield strength, tensile strength and elongation of the steel pipes of examples 1 to 10 and comparative examples 1 to 2 after the heat treatment for tempering were correspondingly tested.
In addition, hardenability of each of the example and comparative example steel pipes after the tempering heat treatment was further tested. The relevant test means are as follows:
hardness test: rockwell hardness tester was used to measure Hardness (HRC) of the steel pipes of examples 1 to 10 and comparative examples 1 to 2 after the tempering heat treatment.
Anti-torsion performance test: the static torsion test apparatus was used to measure the torsion resistance of the steel pipes of examples 1 to 10 and comparative examples 1 to 2 after the heat treatment by tempering.
Table 4 shows the results of performance tests of the high-strength and high-toughness free-cutting seamless steel pipes for motor shafts of examples 1 to 10 and the comparative steel pipes of comparative examples 1 to 2 after heat treatment by tempering.
Table 4.
Note that: in Table 4, rm×A 50 Is the product of tensile strength and elongation.
As can be seen from Table 4, the high strength and toughness free-cutting seamless steel pipes for motor shafts according to examples 1 to 10 of the present invention were significantly superior in combination properties to the comparative steel pipes according to comparative examples 1 to 2 after the heat treatment.
As can be seen from Table 4, the seamless steel pipes for high-strength and high-toughness free-cutting motor shafts of examples 1 to 10 obtained by the invention have excellent mechanical properties, the yield strength Rp0.2 is between 991 and 1195MPa, the tensile strength Rm is between 1289 and 1762MPa, the elongation is between 9 and 14 percent, and the strong plasticity R m ×A 50 Between 14256-24668MPa%, hardness between 55-61HRC, and torsion resistance between 503-599 KN.
In contrast, comparative examples 1 and 2 have lower strength and torsional properties than examples 1 to 10, and the resulting strength and torsional properties do not meet the requirements specified in the present invention.
The design makes at least one mechanical property of the comparative steel pipe prepared in comparative examples 1-2 not reach the requirements of high toughness and free cutting proposed by the patent.
Furthermore, after the completion of the above-mentioned detection of mechanical properties, the inventors also sampled the steel pipes subjected to the tempering heat treatment of each of the examples and comparative examples, and observed and analyzed the microstructure thereof, and the results of the relevant observation and analysis are shown in table 5 below.
Table 5 shows the microstructure observation and analysis results of the high-toughness free-cutting seamless steel pipes for motor shafts of examples 1 to 10 and the comparative steel pipes of comparative examples 1 to 2 after the heat treatment.
Table 5.
As can be seen from the above Table 5, after the tempering heat treatment, the seamless steel pipes for high-strength and high-toughness free-cutting motor shafts of examples 1 to 10 all obtained microstructures of martensite and retained austenite, and the volume phase ratio of the retained austenite was less than or equal to 20%, and the specific volume phase ratio was between 6 and 19%.
Fig. 1 is a photograph showing a metallographic structure of a seamless steel tube for a high-strength and high-toughness free-cutting motor shaft of example 1 after heat treatment.
As shown in fig. 1, in this embodiment, the microstructure of the seamless steel tube for a high-strength and high-toughness free-cutting motor shaft of example 1 after the tempering heat treatment was martensite+retained austenite, and in this embodiment, the volume phase ratio of the retained austenite was 15%.
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 (14)

1. A seamless steel tube for a high-strength and high-toughness free-cutting motor shaft contains Fe and unavoidable impurity elements, and is characterized by further containing the following chemical elements in percentage by mass:
C：0.32～0.48％，0＜Si≤0.20％，Mn：0.5～1.2％，S：0.02～0.10％，Cr：0.6～1.5％，Mo：0.15～0.35％，Cu≤0.25％，Ni≤0.25％，Ce+La≤0.015％，Al：0.015～0.045％，Ca+Mg：0.001～0.006％。
2. the seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 1, wherein the mass percentages of the chemical elements are as follows:
c: 0.32-0.48%, si is more than 0 and less than or equal to 0.20%, mn:0.5 to 1.2 percent, S:0.02 to 0.10 percent, cr:0.6 to 1.5 percent, mo:0.15 to 0.35 percent, cu is less than or equal to 0.25 percent, ni is less than or equal to 0.25 percent, ce+La is less than or equal to 0.015 percent, al:0.015 to 0.045 percent, ca+Mg:0.001 to 0.006 percent; the balance being Fe and unavoidable impurities.
3. The seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 1 or 2, wherein among unavoidable impurities, P is not more than 0.015% and O is not more than 0.0030%.
4. The seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 3, wherein among unavoidable impurities, P is not more than 0.015% and O is not more than 0.0020%.
5. The seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 1 or 2, wherein the mass percentage of each chemical element further satisfies at least one of the following:
C：0.38～0.45％，
0＜Si≤0.15％，
Mn：0.6～0.9％，
S：0.04～0.06％，
Cr：0.8～1.2％，
Cu：0.1～0.25％，
Ni：0.1～0.25％，
Al：0.015～0.035％，
Ce+La：0.001～0.01％，
Ca+Mg：0.001～0.004％。
6. the seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 1 or 2, wherein the microstructure thereof is ferrite+pearlite.
7. The seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 1 or 2, wherein the microstructure subjected to the tempering heat treatment is martensite and retained austenite with a volume phase ratio of 20% or less.
8. The seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 1 or 2, wherein the yield strength is 420-540 MPa, the tensile strength is 550-680 MPa, and the elongation is not less than 20%.
9. The seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to claim 1 or 2, wherein the properties after heat treatment by tempering satisfy: yield strength Rp 0.2 Not less than 960MPa, tensile strength R m 1260MPa or more, elongation A 50 More than or equal to 8 percent, the hardness is more than or equal to 55HRC, the product of strength and elongation is more than 12000MPa, and the torsion resistance is more than or equal to 500KN.
10. A method of manufacturing a seamless steel tube for a high-strength and high-toughness free-cutting motor shaft according to any one of claims 1 to 9, comprising the steps of:
(1) Preparing a tube blank;
(2) Heating, perforating, hot rolling and reducing;
(3) Intermediate heat treatment: annealing the hot rolled pipe material at the temperature of 750-880 ℃ for 30-80 min;
(4) Cold drawing;
(5) And (3) heat treatment of a finished product: normalizing at 800-880 deg.c for 30-60 min to obtain ferrite-pearlite structure.
11. The method according to claim 10, wherein in the step (2), the tube blank is heated and kept at 1220 to 1280 ℃ for 60 to 150 minutes.
12. The method according to claim 10, wherein in the step (2), the perforation temperature is controlled to 1150 to 1250 ℃.
13. The manufacturing method according to claim 10, wherein in the step (2), the hot continuous rolling temperature is controlled to be 1000 to 1200 ℃.
14. The method of claim 10, wherein in step (2), the temperature of the sheet is controlled to be 900 to 1000 ℃.
CN202210690205.1A 2022-06-17 2022-06-17 High-strength and high-toughness seamless steel tube for free-cutting motor shaft and manufacturing method thereof Pending CN117286395A (en)

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JPH11302785A (en) * 1998-04-20 1999-11-02 Sumitomo Metal Ind Ltd Steel for seamless steel pipe
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