CN115679200A - Steel for transmission shaft and manufacturing method thereof - Google Patents
Steel for transmission shaft and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a steel for a transmission shaft, which comprises the following chemical components in percentage by mass: c:0.25 to 0.27%, si:0.25 to 0.35%, mn:0.8 to 0.9%, cr:0.7 to 0.8%, mo:0.35 to 0.45%, nb:0.015 to 0.025%, ni:0.75 to 0.85%, B:0.0008 to 0.0018%, al:0.035 to 0.055%, ti: 0.015-0.025% and Fe not less than 90%. The technical scheme of the invention does not use a large amount of noble metals such as V, co, ni and the like, and can obviously reduce the batch production cost of the steel under the condition of ensuring the high strength and toughness of the steel for the transmission shaft. The invention also discloses a manufacturing method of the steel for the transmission shaft, which comprises the following steps: smelting and casting; heating; forging or rolling; quenching and tempering. The invention adopts the quenching and low-temperature tempering processes, the production process is simple, and the bar obtained by the manufacturing method has excellent mechanical property, narrow hardenability band and wide applicability.
Description
Technical Field
The invention relates to an alloy material and a manufacturing method thereof, in particular to steel for a transmission shaft and a manufacturing method thereof.
Background
Energy conservation, environmental protection and safety are fundamental targets of automobile material development, and the aim of enhancing and reducing weight can be achieved by adopting ultrahigh-strength steel to manufacture automobile parts. The transmission 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, and the tensile strength of the alloy structural steel is lower than 1000MPa when the alloy structural steel is used as a transmission shaft. High-strength transmission shafts above 1000MPa are usually made of structural alloy steel with higher alloy content, such as 18Cr2Ni4WA steel, and when used as a transmission shaft, the tensile strength Rm is more than or equal to 1180MPa (GB/T3077 structural alloy steel), but is difficult to exceed 1300MPa. Since the recent development of transmission devices requires higher power density, the transmission shaft is required to have high strength, and the tensile strength is more than 1500MPa, so that the diameter can be reduced on the premise of transmitting the same power, and 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.
The ultrahigh-strength steel is mainly characterized by high strength and certain toughness, and is mainly used for manufacturing important components which bear high stress and large impact load and have high requirements on fatigue performance. The method has wide application in civil and military fields. However, with the development of application technology and the emphasis on economic acceptance, the ultra-high strength steel is required to have both high toughness and low cost while continuously improving the strength. In the traditional process, in order to obtain the ultrahigh strength steel with higher obdurability, a large amount of Co and Ni must be adopted in alloy components, and the Co can improve the recrystallization temperature of the steel and preserve dislocation structures in addition to the solid solution strengthening effect, so that the nucleation points of fine carbides are increased, more fine carbides are precipitated, and the key effect is played on the ultrahigh obdurability of secondary precipitation strengthened steel; ni can prevent the decomposition of screw dislocation in the matrix and ensure the occurrence of cross slip, which plays a certain role in improving the toughness of the steel. However, co and Ni are rare and precious strategic elements in China, so that the cost is very high and the Co and Ni are difficult to be applied in a large quantity.
For example, chinese patent application CN109504903A describes a low alloy ultra high strength steel, which comprises, by weight, C:0.20 to 0.30%, si:0.50 to 0.70%, mn:0.60 to 0.80%, cr:0.60 to 1.10%, ni:0.40 to 0.65%, mo:0.50 to 0.75%, nb:0.05 to 0.15%, V:0.03 to 0.05%, ti:0.001 to 0.003%, al:0.01 to 0.03%, cu: 0.02-0.05%, P is less than or equal to 0.010%, S: less than or equal to 0.010 percent, and the balance of Fe and inevitable impurities. The strength of the steel grade is improved by adding V element and utilizing the precipitation strengthening effect of V. The obtained ultra-high strength steel has the following mechanical properties: the tensile strength is 1300-1500 MPa, the yield strength is 900-1200 MPa, the elongation is more than or equal to 10%, the impact energy Ak of a room-temperature V-shaped notch Charpy pendulum impact test is more than or equal to 40J, and the Brinell hardness is 390-460HBW. However, V is an element with higher cost, which is not beneficial to reducing the cost, and the steel obtained by the patent can not meet the requirement of higher toughness.
Chinese patent application CN109763063A describes an alloy structural steel suitable for use as a high-strength transmission shaft, which comprises the following chemical components in percentage by weight: c:0.22-0.28%, si:0.10-0.30%, mn:0.50-0.80%, P is less than or equal to 0.005%, S is less than or equal to 0.002%, cr:0.80-1.60%, ni:1.50-2.50%, mo:0.15-0.35%, V:0.10-0.25%, nb is less than or equal to 0.10%, O is less than or equal to 0.0020%, H is less than or equal to 0.0002%, N is less than or equal to 0.0050%, RE:0.0010-0.0035% 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, impact absorption energy KU2 greater than or equal to 78J, bending fatigue strength sigma-1 greater than or equal to 750MPa, torsion fatigue strength tau-1 greater than or equal to 380MPa, and high strength and toughness. In the patent, a large amount of Ni element is added to perform solid solution strengthening, and V element is added to perform precipitation strengthening, so that screw dislocation in a matrix is not easy to decompose by utilizing Ni, the occurrence of cross slip is ensured, and the improvement on the toughness of steel is also performed to a certain extent.
Therefore, it is necessary to develop an ultra-high strength steel having both ultra-high strength and a certain toughness and relatively low use cost by effectively and reasonably utilizing domestic resources.
Disclosure of Invention
In view of the problems of insufficient obdurability of steel for a transmission shaft and cost increase caused by adding V intentionally and adding Co, ni and the like in large quantities in the prior art, the invention provides the steel for the transmission shaft, wherein the steel comprises the following chemical components in percentage by mass: c:0.25 to 0.27%, si:0.25 to 0.35%, mn:0.8 to 0.9%, cr:0.7 to 0.8%, mo:0.35 to 0.45%, nb:0.015 to 0.025%, ni:0.75 to 0.85%, B:0.0008 to 0.0018%, al:0.035 to 0.055%, ti: 0.015-0.025% and Fe not less than 90%. Unless otherwise specified, all numerical ranges of the percentage of each element of the present invention include the endpoints.
According to the technical scheme, a large amount of noble metals such as V, co, ni and the like are not used, the tensile strength is more than or equal to 1500MPa, the yield strength is more than or equal to 1200MPa, and the mass production cost of the steel can be obviously reduced under the condition of ensuring that the steel for the transmission shaft has high strength and toughness.
Further, the steel for a drive shaft of the present invention includes, in mass percent, C:0.25 to 0.27%, si:0.25 to 0.35%, mn:0.8 to 0.9%, cr:0.7 to 0.8%, mo:0.35 to 0.45%, nb:0.015 to 0.025%, ni:0.75 to 0.85%, B:0.0008 to 0.0018%, al:0.035 to 0.055%, ti:0.015 to 0.025%, and the balance of Fe and inevitable impurities.
The design idea of each chemical element in the steel for the transmission shaft is as follows:
c: in the steel for a drive shaft of the present invention, C can improve hardenability of the steel material, so that the steel forms a low-temperature transformation structure having a high hardness in the quenching and cooling process. An increase in the content of C increases the ratio of hard phases such as martensite phase and lower bainite phase, and increases the strength of the steel, but leads to a decrease in toughness. It should be noted that if the content of C element in the steel is too low, the content of low-temperature transformation structures such as martensite and lower bainite is reduced, and the steel cannot obtain a high tensile strength. Based on this, in the steel for a drive shaft of the present invention, the mass percentage of the element C is controlled to be 0.25 to 0.27%.
Si: in the steel for a transmission shaft of the present invention, si substitutes for Fe atoms in the steel in a substitution manner, so that dislocation movement is inhibited, which is beneficial to improving the strength of the steel. Si can reduce the diffusion capability of C in ferrite, so that proper amount of Si can avoid forming coarse carbide and precipitating at defect sites during tempering. However, a higher Si content reduces the impact toughness of the steel. Based on this, in the steel for a drive shaft of the present invention, the mass percentage of the Si element is controlled to be 0.25 to 0.35%.
Mn: in the steel for a power transmission shaft of the present invention, mn exists mainly in a solid solution form. In the quenching process of the steel, mn can inhibit diffusion type phase transformation, the hardenability of the steel is improved, and a low-temperature phase transformation structure is formed, and the structure has higher strength. However, too high a Mn content results in the formation of more retained austenite and a decrease in the yield strength of the steel. Based on this, in the steel for a drive shaft of the present invention, the mass percentage of the Mn element is controlled to be 0.8 to 0.9%.
Cr: in the steel for a drive shaft of the present invention, cr is added to the steel, whereby the steel can suppress the diffusion-type phase transformation, improve the hardenability of the steel, form a hardened martensite structure, and obtain a steel material having a high strength. Meanwhile, in the heating process, if Cr carbide is not completely dissolved, the austenite grain growth can be inhibited. However, if the Cr content is too high, coarse carbides are formed, and the impact properties are deteriorated. Based on this, in the steel for a drive shaft of the present invention, the mass percentage of the Cr element is controlled to be 0.7 to 0.8%.
Mo: in the steel for transmission shafts of the present invention, mo is a ferrite-forming element, which contributes to the improvement of hardenability of the steel, and allows the steel to form bainite and martensite during quenching. If the quenching speed is high and the tempering is carried out in a lower temperature range, mo mainly exists in the steel in a solid solution form, so that the solid solution strengthening effect is achieved; when tempered at a higher temperature, fine carbides are formed, and the strength of the steel is improved. Mo is a precious alloy element, and the cost is increased by adding higher Mo. Based on this, in the steel for a drive shaft of the present invention, the mass percentage of the Mo element is controlled to be 0.35 to 0.45%.
Nb: in the steel for the transmission shaft of the present invention, nb plays a role in suppressing recrystallization of the steel, so that the steel is recrystallized at a relatively low temperature, and austenite grains are refined, thereby achieving the purpose of refining the final structure. Nb carbides and carbonitrides cause interphase precipitation and precipitation from supersaturated ferrite during austenite transformation, thereby causing precipitation strengthening. However, the Nb content is high, and coarse NbC particles are formed under the tempering condition, thereby deteriorating the low-temperature impact energy of the steel. Based on this, in the steel for a propeller shaft of the present invention, the mass percentage of Nb element is controlled to be 0.015 to 0.025%.
Ni: in the steel for transmission shafts of the present invention, ni is present as a solid solution, specifically, as an FCC phase of Fe-Ni-Mn, and thus the stacking fault energy can be reduced and the impact properties of the steel can be improved. Ni is an austenite forming element, too high Ni content can cause too high residual austenite content in steel materials and reduce the strength of the steel, meanwhile, ni is a precious metal, and the mass percent of the Ni element in the steel for the transmission shaft is controlled between 0.75 and 0.85 percent in consideration of the cost of the Ni.
B: in the steel for the transmission shaft of the invention, the B element can be used for replacing carbon and other alloy elements to increase the strength, even if a small amount of boron is added, the strength can be obviously improved, but the B element can be segregated in austenite grain boundaries, and the grain boundary brittleness and the impact toughness of the steel are reduced due to the over-high B content. Based on this, in the steel for a drive shaft of the present invention, the mass percentage of the element B is controlled to be 0.0008 to 0.0018%.
Al: in the steel for the transmission shaft, the Al element can form fine AlN precipitation in the steel making process, and can inhibit the growth of austenite grains in the subsequent cooling process, refine the austenite grains and achieve the effect of fine grain strengthening. It should be noted that the content of Al element in the steel should not be too high, which would lead to the formation of larger Al oxides, and coarse hard inclusions of alumina would deteriorate the fatigue properties of the steel. Based on this, in the steel for a drive shaft of the present invention, the mass percentage of the Al element is controlled to be 0.035 to 0.055%.
Ti: in the steel for transmission shafts of the present invention, ti forms a compound with C and N in the steel, and TiN is formed at a temperature of 1400 ℃ or higher and usually precipitates in a liquid phase or delta ferrite, thereby achieving the purpose of refining austenite grains. Too high Ti content results in the formation of coarse TiN precipitates, which leads to a reduction in the impact and fatigue properties of the steel. During tempering, if the Ti content is too high, the fluctuation range of the impact energy is increased. Therefore, in the steel for a propeller shaft of the present invention, the mass percentage of the Ti element is controlled to be 0.015 to 0.025%.
Further, the steel for a drive shaft of the present invention further includes: calculated by mass percent, cu is less than or equal to 0.05 percent, V is less than or equal to 0.01 percent, ca is less than or equal to 0.002 percent, and N is less than or equal to 0.006 percent.
The steel for the transmission shaft of the present invention further contains elements of Cu, V, ca, and N, and the upper limits of the elements need to be controlled in order to ensure the comprehensive mechanical properties of the steel.
Cu: the hardenability of the steel can be improved by adding Cu into the steel, but the hardenability of the steel is fully considered through the control of elements such as Cr, ni and Mo in the steel for the transmission shaft, the hardenability is too high, and the risk of cracking is caused in the subsequent heat treatment process, so that the mass percent of Cu is strictly limited to be less than or equal to 0.05 percent.
V: v is added into steel to form VC, and the small VC can block dislocation movement and plays a role in dislocation strengthening. If the amount of the element V added is too large, coarse VC particles are formed, and the impact toughness of the steel is lowered. In order to avoid the adverse effect of V on impact toughness and the consideration of cost, the mass percent of V is strictly limited to V less than or equal to 0.01 percent.
Ca: the Ca treatment can improve the casting performance of the steel, but hard calcium aluminate inclusion is easily generated to crack the continuity of a matrix, and the mass percent of Ca is strictly limited to be less than or equal to 0.002 percent in order to control the content of the calcium aluminate inclusion in the steel.
N: n and Ti are preferentially combined in the steel to form TiN, so that the fine-grain strengthening effect is achieved, but the excessive content of N can be combined with B to weaken the strength improving effect of B, and therefore the mass percent of N is strictly limited to be less than or equal to 0.006%.
Further, the steel for a drive shaft of the present invention further includes: calculated by mass percent, the content of P is less than or equal to 0.015 percent, the content of S is less than or equal to 0.005 percent, the content of H is less than or equal to 0.0002 percent, and the content of O is less than or equal to 0.002 percent.
P, S, H and O are all impurity elements in steel, and the content of the impurity elements in the steel is reduced as far as possible in order to obtain steel with better performance and better quality under the permission of technical conditions.
P, S: the impurity element P is easily segregated in the grain boundary, and reduces the bonding energy of the grain boundary, deteriorating the low-temperature impact properties of the steel. The presence of P and Mn increases the temper brittleness of the steel, so that the P content needs to be controlled to be less than or equal to 0.015 percent. In addition, the impurity element S can be combined with Mn in steel to generate MnS, so that the strengthening effect of Mn is weakened, S can be subjected to segregation in the molten steel solidification process to form more sulfide inclusions, and the ultrasonic flaw detection performance and the low-temperature impact performance of the steel are damaged, so that the content of the S element is controlled to be less than or equal to 0.005 percent.
O, H: the O element may form Al with Al and Ti in the steel 2 O 3 TiO, and the like, and in order to ensure the uniformity of steel structure and low-temperature impact energy, the content of O element in the steel needs to be controlled to be less than or equal to 0.002 percent. In addition, H element is subjected to the action of a hydrostatic pressure field of edge dislocation in steel, and can be gathered at a defect position to form hydrogen embrittlement. In the steel with high tensile strength grade, the densities of dislocation, subboundary and the like are high, if the content of the H element in the steel is too high, more H atoms are enriched at the defect part after the quenching and tempering heat treatment of the steel, and the H atoms are aggregated to form H molecules, so that the delayed fracture of the steel is caused. Therefore, the content of the H element is controlled to be H less than or equal to 0.0002 percent in the invention.
Further, the steel for a drive shaft of the present invention: the yield strength is more than or equal to 1200MPa; the tensile strength is more than or equal to 1500MPa; the elongation is more than or equal to 10 percent; the reduction of area is more than or equal to 50 percent; the impact energy KV2 is more than or equal to 20J.
Further, the microstructure of the steel for transmission shafts of the present invention is tempered martensite + retained austenite.
On the other hand, the invention also provides a manufacturing method of the steel for the transmission shaft, which comprises the following steps:
smelting and casting;
heating;
forging or rolling;
and quenching and tempering.
Further, in the heating step, the heating temperature is controlled to 1050 to 1250 ℃.
The heating temperature is controlled to be 1050-1250 ℃ for heating and austenitizing. In this process, carbonitride of Ti, carbide of Mn, cr in the steel may be partially or completely dissolved in austenite. In the subsequent forging or rolling and cooling processes, al and Ti can form fine carbonitride, thereby playing the roles of nailing and rolling austenite crystal boundary and refining the rolled structure of the steel. In addition, mn and Cr elements dissolved in austenite as solid solutions can effectively improve the hardenability of steel. In the subsequent quenching step, mn and Cr elements solid-dissolved in austenite can also improve the martensitic hardenability at the time of quenching.
Further, in the step of forging or rolling, the temperature of finish rolling or finish forging is controlled to be more than or equal to 800 ℃.
The temperature of the final rolling or the final forging is controlled to be more than or equal to 800 ℃, so that the steel can be recrystallized and strain-induced precipitated, and a matrix structure of ferrite and pearlite is formed, and fine carbonitride is precipitated.
Further, in the quenching and tempering steps, the quenching temperature is controlled to be 850-1050 ℃, and the tempering temperature is controlled to be 180-220 ℃.
Specifically, the austenitizing temperature of quenching is 850-1050 ℃, and water quenching is adopted after austenitizing; the tempering temperature is 180-220 ℃, and air cooling or water cooling is carried out after tempering.
The steel material after forging or rolling can be heated to 850-1050 ℃ and quenched after heat preservation. In the heating process, carbonitrides of carbide forming elements Nb, ti, mn and Cr can be completely or partially dissolved, undissolved carbonitrides are nailed and rolled in austenite crystal boundaries, and B is partially aggregated in the austenite crystal boundaries, so that the phenomenon that austenite crystal grains are too coarse is avoided, the purpose of refining the crystal grains after quenching is realized, and the toughness of the steel is improved. In the quenching and cooling process, the alloy elements which are in solid solution in austenite can improve the hardenability of steel, so that the final martensite is finer, and the structure has good obdurability.
The quenched steel can be subjected to low-temperature tempering heat treatment at the tempering temperature of 180-220 ℃, so that the phenomenon of nonuniform internal stress distribution caused by the formation of residual austenite and a martensite structure with high defect density in the quenching process is greatly improved, the residual austenite is decomposed into a two-phase structure of supersaturated alpha solid solution and lamellar carbide in the low-temperature tempering process, and the good toughness of the steel is ensured. The purpose of low-temperature tempering is to reduce the quenching internal stress of steel, reduce the brittleness of the steel and avoid strength reduction caused by high-temperature tempering on the premise of keeping high strength.
By adopting the technical scheme of the invention, through adopting the quenching and low-temperature tempering heat treatment process, a matrix structure of tempered martensite and residual austenite can be formed so as to eliminate the internal stress of steel, so that the obtained bar has good structure uniformity.
The invention has the beneficial effects that:
1. the steel for the transmission shaft is designed by reasonable chemical components, only a small amount of Nb and Ti elements are added, and the purposes of precipitation strengthening and fine grain strengthening are achieved by utilizing the precipitation of carbonitride and the segregation of B in austenite grain boundaries, so that the steel with the yield strength of more than or equal to 1200MPa can be obtained; the tensile strength is more than or equal to 1500MPa; the elongation is more than or equal to 10 percent; the reduction of area is more than or equal to 50 percent; the impact work KV2 is not less than 20J. The steel does not contain a large amount of noble metals such as V, co, ni and the like, can obviously reduce the batch production cost of the steel under the condition of ensuring the high strength and toughness of the steel for the transmission shaft, can be used for replacing the steel for the transmission shaft such as 40Cr, 42CrMo and the like, and achieves the purpose of enhancing and reducing weight. And because the steel for the transmission shaft has good obdurability, the transmission shaft produced in batches by adopting the steel has stable heat treatment quality, high pairing performance between parts of the transmission shaft assembly and long service life, and has good popularization prospect and practical value.
2. The conventional shaft steel usually adopts quenching and tempering heat treatment process of quenching and high-temperature tempering, and aims to form a tempered sorbite, so that the steel has high strength and good plasticity and toughness. The invention adopts the heat treatment process of quenching and low-temperature tempering, the formed matrix structure of tempered martensite and residual austenite reduces the internal stress of the steel on the premise of ensuring high hardness and high strength, so that the obtained steel has excellent strength and certain toughness, the strength reduction caused by high-temperature tempering is avoided, and simultaneously, the low-temperature tempering is more energy-saving and environment-friendly compared with the high-temperature tempering. The manufacturing method of the steel for the transmission shaft has simple production process, and the bar obtained by the manufacturing method has excellent mechanical property, narrow hardenability band and wide applicability.
Drawings
FIG. 1 shows a photograph of the rolled microstructure morphology of the bar of example 1 of the present invention.
Fig. 2 shows a microstructure morphology photograph after heat treatment of the bar of example 1 of the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure. While the invention will be described in conjunction with the preferred embodiments, it is not intended that features of the invention be limited to these embodiments. On the contrary, the invention has been described in connection with the embodiments for the purpose of covering alternatives or modifications as may be extended based on the claims of the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without these particulars. Moreover, some of the specific details have been left out of the description in order to avoid obscuring or obscuring the focus of the present invention. It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
Examples 1 to 6 and comparative example 1
The rods of examples 1-6 were all prepared using the following procedure:
step 1: smelting and casting were carried out according to the chemical composition shown in table 1: smelting by adopting an electric furnace or a converter, and casting into a continuous casting billet or a steel ingot; in the casting process, die casting or continuous casting may be used.
Step 2: heating: the heating temperature is controlled to be 1050-1250 ℃.
And step 3: forging or rolling: the temperature of the finish rolling or the finish forging is controlled to be more than or equal to 800 ℃. However, if forging is performed, the final dimensions such as forging can be performed directly in the forging process. If rolling is carried out, in the rolling process, the billet can be directly rolled to the final specification, or the billet can be rolled to the specified intermediate billet size, and then heating and rolling are carried out to the final finished product size.
And 4, step 4: quenching and tempering: wherein the austenitizing temperature of quenching is 850-1050 ℃, and water quenching is adopted after austenitizing; the tempering temperature is 180-220 ℃, and air cooling or water cooling is carried out after tempering.
The bars of the embodiments 1-6 are all prepared by the steps, and the chemical components and relevant process parameters of the bars meet the design specification control requirements of the invention. The comparative bar of comparative example 1 likewise used: smelting, casting, heating, forging or rolling, quenching and tempering. But the chemical element composition of comparative example 1 has parameters that fail to satisfy the design requirements of the present invention.
It should be noted that the bars of examples 1 to 6 were each made using the steel for transmission shafts of the present invention, and the comparative bar of comparative example 1 was made using a comparative steel.
Table 1 shows the mass percentages of the chemical elements in the steel for transmission shafts of examples 1 to 6 and the comparative steel for comparative example 1.
Table 1 (wt.%, balance Fe and unavoidable impurities other than P, S, H and O)
Table 2 shows the specific process parameters for the rods of examples 1-6 and comparative example 1.
Table 2.
The resulting rods of examples 1-6 and comparative example 1 were sampled and subjected to mechanical property testing, and the results of the property testing are shown in Table 3, respectively, using GB/T228.1-2010 metallic Material tensile test part 1: the test is carried out in the manner of Room temperature test method to detect the tensile strength, yield strength, elongation and reduction of area of the bars of each example and comparative example; the test is carried out by the method of GB/T229-2007 'Metal Charpy notched impact test method' to detect the longitudinal impact energy of the bar materials of each example and comparative example.
Table 3 shows the results of the mechanical properties tests on the bars of examples 1 to 6 and comparative example 1.
Table 3.
As can be seen from Table 3, the yield strength of the bars in the examples 1-6 is not less than 1200MPa, the tensile strength is not less than 1500MPa, the elongation is not less than 10%, the reduction of area is not less than 50%, the impact power KV2 is not less than 20J, and the bars have excellent mechanical properties, the comparative example is the quenched and tempered mechanical property of 40Cr of the steel for the conventional transmission shaft, the reason that the strength difference is large is that the 40Cr is mainly strengthened through solid solution of C and Cr and precipitation of carbide of Cr, but the patent achieves the strengthening purpose by means of microalloying effect of Nb, ti and B besides the strengthening effect of the conventional Cr, ni and Mo alloy elements, and the strength is reduced by higher-temperature tempering at low temperature.
FIG. 1 is a photograph of the rolled microstructure morphology of the bar of example 1. It can be observed that the microstructure of the rolled steel bar of example 1 is a bainite structure.
FIG. 2 is a photograph of the microstructure of the heat-treated bar of example 1. It can be observed that the microstructure of the bar of example 1 after heat treatment was: tempered martensite + retained austenite structure.
In conclusion, the steel for the transmission shaft with high strength, toughness and low cost can be developed by reasonable chemical component design and combined with an optimization process, and the requirements of users on the steel for the transmission shaft with yield strength of more than or equal to 1200MPa, elongation of more than or equal to 10 percent and low cost can be met. Meanwhile, due to good obdurability, the transmission shaft produced by the steel in batch has stable heat treatment quality, high matching performance between parts of the transmission shaft assembly, long service life and good popularization prospect and practical value, and can also be used for replacing transmission shaft steel such as 40Cr, 42CrMo and the like to achieve the purposes of strengthening and reducing weight.
The steel for the transmission shaft can also realize batch commercial production on a bar production line.
The bar made of the steel for the transmission shaft has excellent mechanical property, and the yield strength of the bar is more than or equal to 1200MPa; the tensile strength is more than or equal to 1500MPa; the elongation is more than or equal to 10 percent; the reduction of area is more than or equal to 50 percent; the impact energy KV2 is more than or equal to 20J, and the cost is low.
The manufacturing method adopted by the invention has simple production process, and the bar obtained by the manufacturing method has excellent mechanical property and low and narrow hardenability band, has wide applicability and can bring huge economic benefit.
The combination of the features in the present application is not limited to the combination described in the claims or the combination described in the embodiments, and all the features described in the present application can be freely combined or combined in any manner unless contradicted by each other.
It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.
Claims (10)
1. The steel for the transmission shaft is characterized by comprising the following chemical components in percentage by mass: c:0.25 to 0.27%, si:0.25 to 0.35%, mn:0.8 to 0.9%, cr:0.7 to 0.8%, mo:0.35 to 0.45%, nb:0.015 to 0.025%, ni:0.75 to 0.85%, B:0.0008 to 0.0018%, al:0.035 to 0.055%, ti: 0.015-0.025% and Fe not less than 90%.
2. The steel for a driveshaft according to claim 1, wherein C:0.25 to 0.27%, si:0.25 to 0.35%, mn:0.8 to 0.9%, cr:0.7 to 0.8%, mo:0.35 to 0.45%, nb:0.015 to 0.025%, ni:0.75 to 0.85%, B:0.0008 to 0.0018%, al:0.035 to 0.055%, ti:0.015 to 0.025 percent, and the balance of Fe and inevitable impurities.
3. The steel for the transmission shaft according to claim 1, further comprising, in mass%, not more than 0.05% of Cu, not more than 0.01% of V, not more than 0.002% of Ca, and not more than 0.006% of N.
4. The steel for a driveshaft according to claim 1, wherein the steel for a driveshaft comprises inevitable impurities in a balance, and the inevitable impurities are, in mass%, P is 0.015% or less, S is 0.005% or less, H is 0.0002% or less, and O is 0.002% or less.
5. The steel for a drive shaft according to any one of claims 1 to 4, wherein the steel for a drive shaft has a yield strength of 1200MPa or more; the tensile strength is more than or equal to 1500MPa; the elongation is more than or equal to 10 percent; the reduction of area is more than or equal to 50 percent; the impact energy KV2 is more than or equal to 20J.
6. The steel for a driveshaft according to any one of claims 1 to 4, characterized in that a microstructure of the steel for a driveshaft is tempered martensite + retained austenite.
7. A method for producing a steel for a driveshaft according to any one of claims 1 to 6, characterized by comprising the steps of:
smelting and casting;
heating;
forging or rolling;
quenching and tempering.
8. The method of manufacturing a steel for a driveshaft according to claim 7, wherein a heating temperature is controlled to 1050 to 1250 ℃ in the heating step.
9. The method for producing a steel for a drive shaft according to claim 7, wherein a finish rolling or finish forging temperature is controlled to 800 ℃ or higher in the forging or rolling step.
10. The method of manufacturing a steel for a driveshaft according to claim 7, wherein in the quenching and tempering steps, the quenching temperature is controlled to be 850 to 1050 ℃, and the tempering temperature is controlled to be 180 to 220 ℃.
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| CN102605280A (en) * | 2012-03-15 | 2012-07-25 | 宝山钢铁股份有限公司 | Ultra-thick high-strength high low-temperature toughness steel plates for ocean platforms and production method thereof |
| US20120211132A1 (en) * | 2011-02-18 | 2012-08-23 | Siderca S.A.I.C. | Ultra high strength steel having good toughness |
| CN103205627A (en) * | 2013-03-28 | 2013-07-17 | 宝山钢铁股份有限公司 | Low-alloy high-performance wear-resistant steel plate and manufacturing method thereof |
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2021
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120211132A1 (en) * | 2011-02-18 | 2012-08-23 | Siderca S.A.I.C. | Ultra high strength steel having good toughness |
| CN102605280A (en) * | 2012-03-15 | 2012-07-25 | 宝山钢铁股份有限公司 | Ultra-thick high-strength high low-temperature toughness steel plates for ocean platforms and production method thereof |
| CN103205627A (en) * | 2013-03-28 | 2013-07-17 | 宝山钢铁股份有限公司 | Low-alloy high-performance wear-resistant steel plate and manufacturing method thereof |
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