CN109763063B - Alloy structural steel suitable for high-strength transmission shaft - Google Patents
Alloy structural steel suitable for high-strength transmission shaft Download PDFInfo
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Abstract
An alloy structural steel suitable for being used as a high-strength transmission shaft belongs to the technical field of alloy steel. The weight percentages of chemical components are as follows: 0.22 to 0.28 percent of C, 0.10 to 0.30 percent of Si, 0.50 to 0.80 percent of Mn, less than or equal to 0.005 percent of P, less than or equal to 0.002 percent of S, 0.80 to 1.60 percent of Cr, 1.50 to 2.50 percent of Ni, 0.15 to 0.35 percent of Mo, 0.10 to 0.25 percent of V, less than or equal to 0.10 percent of Nb, [ O ]]≤0.0020，[H]≤0.0002，[N]Less than or equal to 0.0050, RE0.0010-0.0035, and the balance Fe and inevitable impurities. DS inclusion is less than or equal to 1 grade, the size of martensite lath bundle is less than or equal to 5 mu m, the tensile strength is 1500-1700MPa, and the impact absorption energy KU2Not less than 78J, bending fatigue strength sigma‑1Not less than 750MPa, torsion fatigue strength tau‑1380MPa or more, and the fatigue property strength of the steel is improved by more than 20 percent compared with the common transmission shaft steel such as 18Cr2Ni4 WA. The alloy steel has the characteristics of high cleanliness, superfine structure, high strength, high toughness, high bending fatigue strength, high torsional strength and the like.
Description
Technical Field
The invention belongs to the technical field of alloy steel, and particularly relates to alloy structural steel suitable for a high-strength transmission shaft.
Background
The drive shaft is one of the most common basic parts in various mechanical structures and is usually made of alloy structural steel. The commonly used alloy structural steel comprises 40Cr, 42CrMo and the like, when the alloy structural steel is used as a transmission shaft, the tensile strength of the alloy structural steel is lower than 1000MPa, and a high-strength transmission shaft with the tensile strength higher than 1000MPa is commonly made of alloy structural steel with higher alloy content, such as 18Cr2Ni4WA steel.
The 18Cr2Ni4WA steel is a steel grade introduced from the former Soviet Union in the 50 th century, and when the steel is used as a transmission shaft, the tensile strength Rm is more than or equal to 1180MPa (GB/T3077 alloy structural steel), but the tensile strength Rm is difficult to exceed 1300 MPa. Since the latest development of transmission devices requires higher power density, the transmission shaft is required to have high strength, and the tensile strength reaches more than 1500MPa, so that the diameter can be reduced on the premise of transmitting the same power, and the steel grade of the existing alloy structural steel such as 18Cr2Ni4WA steel cannot meet the requirement. Therefore, new propeller shafts require higher strength and fatigue strength structural alloy steels to be manufactured.
On the other hand, the transmission shaft bears periodic load in service, and fatigue fracture is the main failure mode of the transmission shaft, and mainly comprises bending fatigue, torsional fatigue and the like. Bending fatigue Strength σ of 18Cr2Ni4WA Steel-1Not less than 600MPa, torsional fatigue strength tau-1Not less than 300MPa, and the fatigue performance of the transmission can not meet the development requirement of a high-power-density transmission device. Meanwhile, as the tensile strength of the steel is increased, the toughness of the steel for a transmission shaft is generally decreased, and thus the risk of fatigue fracture from internal inclusions is significantly increased. Therefore, the high-strength steel for transmission shafts must consider ensuring that toughness is not lowered while strength is increased, and how to further ensure improvement in fatigue properties by increasing cleanliness.
It has been shown in the research that refining the size of prior austenite grains and martensite lath bundles can significantly improve the toughness of high strength structural alloy steel (Chunfang Wang, Maoqiu Wang, Jie Shi, et al. effective against microstructural refining on the basis of the steel of low carbon steel. script Materialia,2008,58(6): 492) and thus also improve the fatigue properties (Wangbin, Wang Mao ball, Li Zhenhua, et al. influence of grain size on the fatigue limit of surface carburized steel. report of iron and steel research, 2010,22(11): 23-27). In addition, large-size oxide inclusions are often used as Fatigue crack sources in high-strength steels, resulting in a decrease in Fatigue properties (Yan Liu, Maoqiu Wang, Jie Shi, et al. Fatisue properties of two cases hardingsteels after car certification. International Journal of Fatisue, 2009,31(2): 292-.
Disclosure of Invention
The invention aims to provide an alloy structural steel suitable for a high-strength transmission shaft and a high-performance transmission shaft steel, wherein P is less than or equal to 0.005 percent, S is less than or equal to 0.002 percent, and [ O ]]Not more than 0.0020 percent, DS inclusion not more than 1 grade, martensite lath bundle size not more than 5 mu m, tensile strength of 1500-1700MPa, and impact absorption energy KU2Not less than 78J, bending fatigue strength sigma-1Not less than 750MPa, torsion fatigue strength tau-1380MPa or more, and the fatigue property strength of the steel is improved by more than 20 percent compared with the common transmission shaft steel such as 18Cr2Ni4 WA.
The alloy steel has the characteristics of high cleanliness, superfine structure, high strength, high toughness, high bending fatigue strength, high torsional strength and the like, and has the P content of less than or equal to 0.005 percent, the S content of less than or equal to 0.002 percent and the content of [ O ]]Not more than 0.0020 percent, DS inclusion not more than 1 grade, martensite lath bundle size not more than 5 mu m, tensile strength Rm not less than 1500MPa, impact absorption energy KU2Not less than 78J, bending fatigue strength sigma-1Not less than 750MPa, torsion fatigue strength tau-1Not less than 380 MPa. The material is extremely suitable for the service condition of a high-torque transmission shaft, and the fatigue performance and strength of the material are improved by more than 20 percent compared with the common transmission shaft steel such as 18Cr2Ni4WA and the like.
High-strength shaft steel such as 18Cr2Ni4WA steel is used after quenching and low-temperature tempering heat treatment, and the structure thereof is tempered martensite. The strength level of the low-temperature tempered martensitic steel is directly related to the carbon content in the steel, so in order to improve the strength of the steel for the transmission shaft to the level of 1500MPa in total, the increase of the carbon content in the steel needs to be considered firstly. However, as the carbon content increases and the strength increases, the toughness of the steel generally decreases significantly. Therefore, it is required to improve the toughness of steel for transmission shafts by refining the structure of steel and improving the cleanliness of steel while improving the strength. In terms of fatigue properties, control of the size of inclusions, particularly oxide-based inclusions, needs to be considered. Therefore, control of the oxygen content in steel is critical.
According to the above purpose, the technical scheme adopted by the invention is as follows: (1) the content of C element is controlled to ensure the content of solid-solution carbon in the martensite structure after low-temperature tempering, and the strength of more than 1500MPa is achieved by utilizing the solid-solution strengthening effect; (2) the microstructure is refined through microalloying, so that the prior austenite crystal grain is controlled below 20 mu m, and the size of a martensite lath bundle is controlled below 5 mu m, thereby improving the toughness; (3) the toughness is further improved by controlling the cleanliness, particularly controlling the S content to be below 0.002 percent and the P content to be below 0.005 percent; (4) by adopting a protective atmosphere electroslag remelting process, the oxygen content in steel is less than or equal to 20ppm, DS type inclusions are less than or equal to 1 level (the size is less than or equal to 27 mu m), and the fatigue performance is obviously improved; (5) by adding the RE element, the sulfide is made harmless, thereby further improving the toughness.
The steel comprises the following specific chemical components in percentage by weight: 0.22 to 0.28 percent of C, 0.10 to 0.30 percent of Si, 0.50 to 0.80 percent of Mn, less than or equal to 0.005 percent of P, less than or equal to 0.002 percent of S, 0.80 to 1.60 percent of Cr, 1.50 to 2.50 percent of Ni, 0.15 to 0.35 percent of Mo, 0.10 to 0.25 percent of V, less than or equal to 0.10 percent of Nb, less than or equal to 0.0020 percent of [ O ], lessthan or equal to 0.0002 percent of [ H ], lessthan or equal to 0.0050 percent of [ N ], 0.0010 to 0.0035 percent of RE, and the balance of Fe and inevitable impurities.
The action and the proportion of each element are as follows:
c: the solid solution strengthening element plays a role in determining the strength of the quenched martensitic steel. In order to ensure that the tensile strength of the steel for the transmission shaft after quenching and low-temperature tempering reaches 1500MPa, the content of C needs to be controlled to be more than 0.22 percent, and the ductility and toughness are reduced due to the overhigh content of C. Therefore, the C content should be controlled to 0.22-0.28%.
Si: as the deoxidizing element, it may cause a decrease in ductility and toughness. When the content of Si is below 0.10%, the effective deoxidation effect cannot be realized; when the Si content is more than 0.30%, the ductility and toughness may be affected. Therefore, the Si content should be controlled to 0.10-0.30%.
Mn: as effective elements for deoxidation and desulfurization, the active elements are added during smelting. But also reduces the toughness and plasticity of the martensitic steel. Therefore, in order to ensure the deoxidation effect and improve the ductility and toughness, the Mn content should be controlled to be 0.50-0.80%.
P: micro segregation is formed when molten steel is solidified, and then the micro segregation is deviated to a grain boundary when the molten steel is heated at a temperature after austenite, so that the brittleness of the steel is remarkably increased, and the toughness is reduced. Considering that the increase of P content brings increased difficulty and cost, P content should be controlled below 0.005%.
S: the formation of MnS inclusions and segregation at grain boundaries deteriorate the toughness of the steel, thereby reducing the plasticity of the steel. Considering that the production cost is increased by increasing the S content, the S content is preferably controlled to be 0.002% or less.
Cr: improving hardenability, strength and plastic toughness. The above effect is not significant when the content is less than 0.80%, and the increase is not significant when the content is more than 1.60%. Therefore, the Cr content should be controlled to 0.80-1.60%.
Ni: the toughness is improved, and meanwhile, the austenite forming element is beneficial to keeping certain residual austenite, so that the plastic toughness is improved. The ductility and toughness required for a tensile strength of 1500MPa cannot be ensured at a content of less than 1.50%, and the effect is not remarkably increased at a content of more than 2.50%, resulting in an increase in cost. Therefore, the Ni content should be controlled to 1.50-2.50%.
Mo: improving hardenability and purifying crystal boundary. When the Mo content is less than 0.15%, the secondary hardening effect is insufficient, but when it is more than 0.35%, the toughness and plasticity are remarkably lowered. Therefore, the Mo content should be controlled to 0.15-0.35%.
V: in the presence of fine carbon (nitride) formation, the crystal grains can be refined, thereby improving the toughness of the steel. The addition of a proper amount can improve the performance, and when the content is higher than 0.25%, large-particle carbon (nitrogen) compounds are easily formed, so that the toughness and the plasticity are reduced, and the cost is obviously increased. Therefore, the V content should be controlled to 0.10-0.25%.
Nb: the micro alloying elements are added to form an NbC precipitated phase, so that grains can be refined, and the toughness of the steel is improved. It can be added in a proper amount to improve the performance, and too high results in a significant increase in cost. Therefore, the Nb content should be controlled to be less than or equal to 0.10%.
[ O ]: harmful elements in the steel form oxide inclusions, which seriously affect the fatigue properties of the high-strength steel. The lower the oxygen content, the higher the probability of large-size inclusions. The size of inclusions can be reduced to some extent by the electroslag remelting process, but may result in an increase in oxygen content. The oxygen content can be controlled to be less than or equal to 15ppm by electric furnace smelting, and the oxygen content can be controlled to be less than or equal to 20ppm after electroslag remelting. At this time, the inclusion Ds can be less than or equal to 1 grade (the size is less than or equal to 27 mu m) by combining the electroslag remelting process technology.
[H] The method comprises the following steps Harmful elements in the steel can generate defects such as white spots and the like when the content of the harmful elements is too high, and can also cause brittleness, and the content of the harmful elements can be controlled to be less than or equal to 2ppm after the harmful elements are remelted by electroslag in protective atmosphere.
[ N ]: too high can reduce the high-temperature plasticity of the steel, thereby affecting the hot workability, and can be controlled to be less than or equal to 50ppm after being remelted by electroslag in protective atmosphere.
RE: deoxidation and desulfurization, and denaturalizing inclusions, thereby enabling to improve the plasticity of the steel. The effect is not obvious when the content is less than 0.0010%, and the effect is not obviously increased when the content is more than 0.0035%, so that the saturation is achieved. Therefore, the content of RE should be controlled to 0.0010-0.0035%.
Drawings
FIG. 1 is a view of a rotary bending fatigue test specimen.
FIG. 2 is a view of a torsional bending fatigue test specimen.
Detailed Description
The high-strength transmission shaft steel can be produced by adopting an electric furnace, external refining, electrode casting, electroslag remelting, forging/rolling and annealing process, and can be used for a high-strength transmission shaft after austenitizing at 880 +/-20 ℃ and tempering at 200 +/-20 ℃.
Compared with the prior 18Cr2Ni4WA steel, the tensile strength of the steel of the invention is improved from 1200MPa to 1500-1700MPa, and the steel has good toughness (KU)2Not less than 78J) and fatigue performance (bending fatigue strength sigma)-1Not less than 750MPa, torsion fatigue strength tau-1Not less than 380MPa), thereby providing a foundation for high-strength transmission and high-safety service.
Examples
Preparing materials: according to the designed chemical composition range, the specific chemical compositions of the steel (furnace number 1-5) produced by adopting an electric furnace (EAF), refining (LF and VD), smelting, pouring an electrode, electroslag remelting in protective atmosphere, forging/rolling and annealing process and the steel (furnace number 6-7) produced by adopting the steel and the furnace 2 are shown in the table 1. Samples were taken (and heat treated) on a round bar test material of 100mm phi for inclusion, microstructure, mechanical properties and fatigue properties.
The tensile and impact properties are that a bar material with the diameter of phi 20mm is subjected to rough machining, austenitization at the temperature of 880 +/-20 ℃ for × 30 minutes, oil quenching, tempering at the temperature of 200 +/-20 ℃ for 2 hours, air cooling and further processing into a standard room temperature tensile sample (L)0＝5d0，d05mm) and a Charpy U-shaped impact test specimen (10mm × 10mm × 55mm), and corresponding tests are carried out according to the national standard, the tensile and impact mechanical properties are shown in Table 2, it can be seen that the tensile strength of the invented steel is in the range of 1500-1700MPa, and the impact absorption energy is obviously higher than that of 18Cr2Ni4WA comparative steel.
Fatigue performance: a bar with the diameter of 20mm is subjected to rough machining, austenitizing at 880 +/-20 ℃ for 30 minutes, oil quenching, tempering at 200 +/-20 ℃ for 2 hours, air cooling and then processing into a rotary bending fatigue sample shown in figure 1 and a torsional fatigue sample shown in figure 2. And a lifting method is adopted according to the national standard to carry out a rotary bending fatigue test and a torsional fatigue test, and the fatigue limit result is shown in table 2. It can be seen that the bending fatigue limit and the torsional fatigue limit of the inventive steel are both improved by 20% or more under the condition that the tensile strength is improved to 1500MPa or more, as compared with the comparative steel of 1200 MPa.
Table 1 chemical composition and inclusion size, wt% of examples and comparative steels
TABLE 2 microstructure and mechanical Properties of the examples and comparative steels
Claims (1)
1. An alloy structural steel suitable for being used as a high-strength transmission shaft is characterized by comprising the following chemical components in percentage by weight: 0.22 to 0.28 percent of C, 0.10 to 0.30 percent of Si, 0.50 to 0.80 percent of Mn, less than or equal to 0.005 percent of P, less than or equal to 0.002 percent of S, 0.80 to 1.60 percent of Cr, 1.50 to 2.50 percent of Ni, 0.15 to 0.35 percent of Mo, 0.12 to 0.25 percent of V, less than or equal to 0.10 percent of Nb, less than or equal to 0.0020 percent of [ O ], lessthan or equal to 0.0002 percent of [ H ], lessthan or equal to 0.0050 percent of [ N ], 0.0010 to 0.0035 percent of RE, and the balance of Fe and inevitable impurities;
the alloy structural steel has DS inclusion less than or equal to 1 grade, martensite lath bundle size less than or equal to 5 microns, tensile strength Rm greater than or equal to 1500MPa, and impact absorption energy KU2Not less than 78J, bending fatigue strength sigma-1Not less than 750MPa, torsion fatigue strength tau-1≥380MPa；
The alloy structural steel is suitable for the service condition of a high-torque transmission shaft, and the fatigue performance and strength of the alloy structural steel are improved by more than 20 percent compared with those of the steel for a common transmission shaft of 18Cr2Ni4 WA.
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| CN112831723B (en) * | 2020-12-31 | 2022-05-10 | 钢铁研究总院 | High-temperature carburization resistant gear steel with large crystal grains and control method |
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| JP2001234277A (en) * | 2000-02-23 | 2001-08-28 | Nippon Steel Corp | High-strength steel excellent in fatigue characteristics and method for producing the same |
| JP2012188729A (en) * | 2010-05-27 | 2012-10-04 | Jfe Steel Corp | Electric-resistance-welded steel pipe with excellent torsion fatigue resistance and process for producing the same |
| CN105324502A (en) * | 2013-06-07 | 2016-02-10 | 新日铁住金株式会社 | Heat-treated steel material and manufacturing method thereof |
| CN108441758A (en) * | 2018-02-12 | 2018-08-24 | 中国铁道科学研究院金属及化学研究所 | A kind of high-speed EMUs axle steel and preparation method thereof suitable for extremely frigid zones |
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|---|---|---|---|---|
| JP2001234277A (en) * | 2000-02-23 | 2001-08-28 | Nippon Steel Corp | High-strength steel excellent in fatigue characteristics and method for producing the same |
| JP2012188729A (en) * | 2010-05-27 | 2012-10-04 | Jfe Steel Corp | Electric-resistance-welded steel pipe with excellent torsion fatigue resistance and process for producing the same |
| CN102906293A (en) * | 2010-05-27 | 2013-01-30 | 杰富意钢铁株式会社 | Electric-resistance-welded steel pipe with excellent torsion fatigue resistance and process for producing same |
| CN105324502A (en) * | 2013-06-07 | 2016-02-10 | 新日铁住金株式会社 | Heat-treated steel material and manufacturing method thereof |
| JPWO2014196645A1 (en) * | 2013-06-07 | 2017-02-23 | 新日鐵住金株式会社 | Heat treated steel and method for producing the same |
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