JP3607583B2 - Steel for power transmission parts and power transmission parts - Google Patents

Description

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【表２】

【００２８】
【表３】

【００２９】
【表４】

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【表５】

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【発明の効果】
本発明は潤滑油を介して接触し，その摩擦力を利用することで動力伝達を行う動力伝達部品用鋼および動力伝達部品に関して，溶製時の適正な化学成分と熱処理後の固溶Ｃ量と硬さを制御することにより，摩擦力により動力を伝達する部品に関して，一般的に用いられるＳＵＪ２，ＳＣＭ４２０および他の従来鋼に対して，十分な接触疲労特性向上効果を確保するものである。
【図面の簡単な説明】
【図１】本発明の接触疲労特性を測定する接触疲労試験機の概要を示す。
【図２】表３における熱処理のうち，高周波焼入に関するヒートパターンを示す。
【図３】表３における熱処理のうち，一部の浸炭に関するヒートパターンを示す。
【図４】表３における熱処理のうち，一部の浸炭に関するヒートパターンを示す。
【符号の説明】
１．．．駆動ローラ，
２．．．円盤状試験片（従動円盤），
２１．．．接触面，
３．．．駆動モータ，
４．．．動力吸収機，[0001]
【Technical field】
The present invention exhibits good contact fatigue characteristics with respect to parts that transmit power by contact frictional force, such as steel and parts used in toroidal continuously variable transmissions, etc., through lubricating oil having a large friction coefficient. We propose steel for power transmission parts and power transmission parts using the steel.
[0002]
[Prior art]
Generally, gears and bearings are used as parts used in automobiles, industrial machines, etc. and subjected to contact fatigue. Gears are used as power transmission parts, especially in automobile transmissions, and bearings are used in support parts of rotating bodies, and it is important to reduce frictional force due to contact that causes power loss.
[0003]
In recent years, as an alternative to this gear-type transmission, a droidal continuously variable transmission has begun to be adopted. This toroidal continuously variable transmission does not transmit power by mechanical meshing of gears, but a driving side rotating body (referred to as a disk-shaped part or disk) and a driven side rotating body (referred to as a disk-shaped part or disk). A plurality of rollers are arranged between the two and rotated by the frictional force generated at each contact portion to transmit power. Therefore, since the roller rolls on the disk-shaped part, a spin slip occurs at the contact portion, and heat is generated. Further, a large frictional force is generated on the contact portion surface that is not in a normal rolling contact to transmit power. . For this reason, it is considered that the steel used for component parts is a very harsh environment compared to bearings. Here, the spin slip means a slip generated from a difference in peripheral speed in the contact surface when the roller rolls on the disk-shaped part.
[0004]
Conventionally, case-hardened steel represented by SCR420 and SCM420 and high carbon chromium bearing steel represented by SUJ2 are mainly used for gears and bearings with contact fatigue. However, when these steels are used in applications such as toroidal-type continuously variable transmissions, there is a problem of causing early breakage. Thus, there is a demand for steel having good contact fatigue characteristics and parts using the steel under such a special use environment.
[0005]
[Problems to be solved]
To date, steels proposed under such circumstances have been disclosed in JP-A-8-326862, JP-A-10-103440, and the like. For example, Japanese Patent Laid-Open No. 8-326862 uses induction hardening as a surface hardening treatment, but the fatigue life improving effect is not sufficient for this application. Japanese Patent Laid-Open No. 10-103440 employs carburizing as the surface hardening treatment, but the methods including carburizing and carbonitriding have not been able to obtain a sufficient fatigue life improving effect. However, there is a problem that enormous amount of time and energy are required, and environmental problems such as CO2 emission occur at the same time.
[0006]
In view of these problems, the object of the present invention is to achieve a high surface pressure, a high frictional force, a high frictional force and a high temperature in the ordinary quenching tempering or induction quenching as a heat treatment. An object of the present invention is to provide a power transmission component steel and a power transmission component that exhibit good contact fatigue characteristics with respect to a power transmission component that becomes a harsh environment, such as a toroidal continuously variable transmission.
[0007]
[Means for solving problems]
As a result of intensive studies, the inventors have found that C: more than 0.65 to 0.90 wt%, Si: more than 0.5 to 2.0 wt%, and Mn: 1.0 wt% in order to solve the above problems. Hereinafter, P: 0.025 wt% or less, S: 0.035 wt% or less, Cu: 0.3 wt% or less, Cr: more than 4.0 to 6.0 wt%, Al: 0.05 wt% or less, O: 0.0. A steel which is formed by spheroidizing a steel containing Fe and unavoidable impurities, and containing a part containing this steel. When tempering is performed, the solid solution C content in the matrix excluding the undissolved carbide of the part is more than 0.40 to 0.65 wt%, and the hardness of the part is Hv 700 or more. Furthermore, Ni: 1.0% or less, Mo: 1.0% or less Providing steel for power transmission components that can contain seeds and two types, and that can use high-frequency induction heating for quenching and tempering and that transmits power by frictional force with good contact fatigue characteristics To do.
[0008]
Furthermore, C: more than 0.65 to 0.90 wt%, Si: more than 0.5 to 2.0 wt%, Mn: 1.0 wt% or less, P: 0.025 wt% or less, S: 0.035 wt% Hereinafter, Cu: 0.3 wt% or less, Cr: more than 4.0 to 6.0 wt%, Al: 0.05 wt% or less, O: 0.0015 wt% or less, N: 0.030 wt% or less, Ti: 0.0. After quenching and tempering a part made of spheroidized steel containing 005 wt% or less, the balance being Fe and unavoidable impurities, the amount of solute C in the matrix excluding undissolved carbide of the part Is more than 0.40 to 0.65 wt%, and the hardness of the component is Hv 700 or more, and further, one of Ni: 1.0% or less, Mo: 1.0% or less, and It can contain two types, and further relates to quenching and tempering It can be used a high-frequency induction heating, to provide a power transmission part for transmitting power by frictional force with good contact fatigue properties.
[0009]
The reason for limitation of each alloy element is demonstrated below.
C: Over 0.65 to 0.90 wt%
C is an indispensable element for maintaining the strength of steel, and in order to obtain the required hardness after leaving undissolved carbide after quenching and tempering treatment, the content of C exceeds 0.65 wt%. A quantity is needed. However, if the content is too large, large eutectic carbides and net-like carbides are likely to precipitate at grain boundaries, and the upper limit is set to 0.90 wt. %. Preferably 0.70 to 0.80 wt% is desirable.
[0010]
Si: more than 0.5 to 2.0 wt%
Si is one of the important elements for the present invention, and the inventors found not only the resistance to tempering and softening but also the effect of suppressing the deterioration of the contact fatigue characteristics in the parts that transmit power by the contact friction force. . For that effect, a content exceeding 0.5 wt% is required. However, adding excessive amounts not only saturates the effect, but also raises the transformation point of the steel, so that the heat treatment temperature must be increased, and the forging and cold workability are impaired. The upper limit of Si content is 2.0 wt%. Preferably 1.1 to 1.7 wt% is desirable.
[0011]
Mn: 1.0 wt% or less Mn is an element that improves the toughness and hardness of the base martensite by improving the hardenability of the steel. However, if added excessively, softening annealing of the material becomes difficult, and workability and heat The upper limit is made 1.0 wt% in order to deteriorate the inter-workability.
P: 0.025 wt% or less P is an element that segregates at the grain boundaries and causes embrittlement of the grain boundaries when present in a large amount in steel. Therefore, it is desirable that it is as low as possible, and the upper limit is regulated to 0.025 wt%.
S: 0.035 wt% or less S is an element that improves machinability, but if added in a large amount, large metal non-inclusions such as MnS are generated, and the upper limit is set to 0.035 wt% to deteriorate fatigue characteristics. .
[0012]
Cu: 0.3 wt% or less Cu is an element that improves the hardenability and corrosion resistance of steel. However, in the present invention, if its content is too large, problems such as red heat embrittlement occur and the productivity deteriorates. The upper limit is 0.3 wt%.
Ni: 1.0 wt% or less Ni is an element effective in improving fatigue characteristics in that it strengthens the matrix in steel and improves toughness. However, if the content is increased, the effect is saturated and cold workability is inhibited, the amount of retained austenite increases during quenching, the hardness decreases to deteriorate the fatigue characteristics, and further increases the material cost. Therefore, the content is 1.0 wt% or less.
[0013]
Cr: 4.0-6.0 wt%
Cr is one of the elements essential for the present invention, and not only provides resistance to temper softening, but also provides wear resistance by forming carbides. In the present invention, Cr is added simultaneously with Si, We found an effect to suppress deterioration of contact fatigue characteristics in parts that transmit power by contact friction force. For that effect, it is necessary to add over 4.0 wt%. However, even if added excessively, the effect is saturated. Rather, precipitation may result in the precipitation of huge carbides, which may deteriorate the fatigue characteristics. 0 wt%.
[0014]
Mo: 1.0 wt% or less Mo is a carbide forming element like Cr, affects hardness and wear resistance, and further improves temper softening resistance. In the present invention, it can be added because it has been found that the contact fatigue characteristics can be further improved by the addition. However, since Mo forms a more stable carbide than Cr, increasing its content promotes the formation of large eutectic carbides that degrade fatigue properties, and further secures a solid solution C content. By increasing the quenching temperature, the heat treatment cost is increased and the steel productivity such as hot workability is adversely affected.
[0015]
Al: 0.05 wt% or less Al is unavoidable because it is used as a deoxidizer in the production of steel, and is known to bind to N and suppress the growth of crystal grains, If added excessively, it tends to be oxide inclusions and adversely affects contact fatigue characteristics, so the upper limit is made 0.05 wt%.
O: 0.0015 wt% or less O is an element that forms hard non-metallic inclusions that cause a decrease in contact fatigue characteristics by bonding with Al. Therefore, it is desirable that O be as low as possible. 0.0015 wt% or less Regulated.
[0016]
N: 0.030 wt% or less N is known to bind to Al and suppress the growth of crystal grains, and can be added for its effect, but if added excessively, casting defects Therefore, the upper limit of the content is set to 0.030 wt%.
Ti: 0.005 wt% or less Ti binds to N and easily forms large and hard non-metallic inclusions and degrades contact fatigue characteristics. did.
Solid solution C amount in matrix after quenching: more than 0.40 to 0.65 wt%
In the present invention, it has been found that the amount of dissolved C in the matrix when quenching and tempering a part affects the contact fatigue characteristics when power is transmitted by frictional force. In order to improve this, the amount of dissolved C needs to be in the range of more than 0.40 to 0.65 wt%. If it becomes 0.40 wt% or less, the quenching and tempering hardness decreases and the contact fatigue characteristics are deteriorated. If the amount of solute C exceeds 0.65 wt%, for example, the necessary hardness can be maintained. However, since it was found that the contact fatigue characteristics were deteriorated, the upper limit was set to 0.65 wt%. Preferably 0.45 to 0.60 wt% is desirable.
[0017]
Quenching and tempering hardness: Hv700 or higher Since the target part according to the present invention receives a contact load, it is necessary to prevent plastic deformation and withstand the surface pressure, so the lower limit is set to Hv700.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The inventors considered that it was necessary to carry out a test that reproduced the environment in which the target steel or part was used in order to achieve the present invention. That is, the test must take into account high surface pressure, power transmission by frictional force, high temperature, and spin slip in the contact surface.
[0019]
FIG. 1 shows a contact fatigue tester used in a test according to the present invention. In this testing machine, a power absorber 4 is used in order that two or three driving rollers 1 receiving a vertical load roll on a disk-shaped test piece (driven disk) 2 by a driving motor 3 to give a sufficient frictional force. The driven disk 2 that is being braked is driven by using the frictional force generated on the contact surface 21.
[0020]
Table 1 shows the characteristics of this testing machine, a roller pitching testing machine generally used as a substitute evaluation of gears, and a thrust type rolling life testing machine used as a substitute evaluation of bearings. From Table 1, this testing machine is suitable for evaluating parts that transmit power by contact friction force with spin slip.
Table 2 shows a list of chemical components of the test materials that have been subjected to various studies in order to achieve the present invention. These specimens are melted with VIM, and after batch rolling, they are shaped by hot forging and upsetting forging, and spheroidized to reduce hardness and facilitate machining. As annealing, after holding at 850 ° C. for 5 hours, and then gradually cooling to 550 ° C. at 15 ° C./hr, it was machined to a predetermined size and subjected to a predetermined quenching heat treatment. Furthermore, the surface and the decarburized layer were removed by finishing the surface and used for the test.
[0021]
Table 3 shows the amount of solute C and surface hardness in the matrix of the surface after heat treatment (details of heat treatment are described in Table 4, FIG. 2, FIG. 3 and FIG. 4), and finish processing. . In FIG. 3 and FIG. P. Means the carbon potential in a carburizing atmosphere. Here, the amount of dissolved C was determined from the measurement of the lattice constant of γ (220) by X-ray diffraction, and the surface hardness was measured with a 10 kg Vickers hardness tester. The measurement was performed on the contact surface 21 of the disk-shaped test piece (driven disk) 2 with the driving roller 1.
These specimens were tested in the contact fatigue tester shown in FIG. 1 under the conditions shown in Table 5, and the contact fatigue characteristics were measured as the number of revolutions until the occurrence of peeling damage on the contact surface. The results are shown in Table 6, where the average life ratio is expressed as a ratio where steel R (JIS-SUJ2) is 1.
[0022]
Examples according to the present invention will be described below. The steels of the present invention are steels A to J in Table 2. Steels E2 and E3 in Table 3 are obtained by changing the heat treatment conditions for steel E and changing the amount of solid solution C and hardness in the matrix. is there. Steel H2 in Table 3 uses induction hardening for the heat treatment of steel H. It can be seen that these steels of the present invention have good contact fatigue characteristics with an average life ratio shown in Table 6 of 4.1 to 6.2.
[0023]
On the other hand, the comparative steels are steel K to steel P in Table 2, and steel K has a larger C content and steel N has a lower C content than the steel of the present invention, and is sufficient as shown in Table 6. The life cannot be improved, and the steel L has a lower Si content and the steel M has a lower Cr content than the steel according to the present invention. Furthermore, steel O has a higher Ti content than the steel of the present invention, and is considered to have more non-metallic inclusions, so a sufficient effect is not obtained.
Here, the chemical composition of the steel P is within the scope of the present invention, but the steel P, P2, and P3 in Table 3 are the heat treatment conditions of (4), (5), and (6) in Table 4, respectively. Steel P has a high quenching temperature and a large amount of solute C in the matrix, and Steel P2 has a low quenching temperature and a small amount of solute C in the matrix. Steel P3 has a solute C content in the matrix within the range of the present invention, but has a high tempering temperature and a hardness lower than the range of the present invention. Therefore, regarding these steels P to P3, as shown in Table 6, a sufficient life improvement is not obtained as compared with the steel of the present invention.
[0024]
Further, steels Q to T in Table 2 show conventional steels, and Table 3 shows the heat treatment, the amount of dissolved C in the matrix, and hardness. Here, the steel Q is JIS-SUJ2, the steel R is JIS-SCM420, the steel S corresponds to JP-A-8-326862, and the steel T corresponds to JP-A-10-103440. None of the conventional steels has a lower alloy amount than the steel of the present invention, and the carburized steel R and steel T have a high amount of solute C in the matrix, and as shown in Table 6, a sufficient improvement in life has not been obtained. The results of these comparative steels and conventional steels show the validity of the invention.
[0025]
Although the embodiment of the present invention has been described in detail above, this is merely an example, and can be applied to steel for power transmission parts and power transmission parts that transmit power by frictional force without departing from the intention of the present invention. is there.
[0026]
[Table 1]

[0027]
[Table 2]

[0028]
[Table 3]

[0029]
[Table 4]

[0030]
[Table 5]

[0031]
[Table 6]

[0032]
【The invention's effect】
The present invention relates to steel for power transmission parts and power transmission parts that contact with each other via lubricating oil and transmit power by utilizing the frictional force, and appropriate chemical components at the time of melting and the amount of solute C after heat treatment. By controlling the hardness, it is possible to secure a sufficient effect of improving contact fatigue characteristics with respect to parts that transmit power by frictional force as compared to SUJ2, SCM420 and other conventional steels that are generally used.
[Brief description of the drawings]
FIG. 1 shows an outline of a contact fatigue testing machine for measuring contact fatigue characteristics of the present invention.
FIG. 2 shows a heat pattern related to induction hardening among the heat treatments in Table 3.
FIG. 3 shows a heat pattern related to partial carburization in the heat treatment in Table 3.
FIG. 4 shows a heat pattern related to partial carburization in the heat treatment in Table 3.
[Explanation of symbols]
1. . . Driving roller,
2. . . Disk-shaped specimen (driven disk),
21. . . Contact surface,
3. . . Drive motor,
4). . . Power absorber,

Claims (6)

C: more than 0.65 to 0.90 wt%, Si: more than 0.5 to 2.0 wt%, Mn: 1.0 wt% or less, P: 0.025 wt% or less, S: 0.035 wt% or less, Cu: 0.3 wt% or less, Cr: more than 4.0 to 6.0 wt%, Al: 0.05 wt% or less, O: 0.0015 wt% or less, N: 0.030 wt% or less, Ti: 0.005 wt% or less Contained in the steel, which consists of Fe and unavoidable impurities in the form of spheroidizing, and when the parts made of this steel are quenched and tempered, the solid solution in the matrix excluding the insoluble solid carbide For power transmission components that transmit power by frictional force with good contact fatigue characteristics, characterized in that the amount of C is more than 0.40 to 0.65 wt% and the hardness of the component is Hv 700 or more steel. In Claim 1, it contains further 1 type and 2 types of Ni: 1.0% or less, Mo: 1.0% or less, and the remainder consists of Fe and an unavoidable impurity, Good Steel for power transmission parts that transmits power by frictional force with excellent contact fatigue characteristics. The steel for power transmission parts according to claim 1 or 2, wherein power is transmitted by frictional force having good contact fatigue characteristics using high frequency induction heating for quenching and tempering. C: more than 0.65 to 0.90 wt%, Si: more than 0.5 to 2.0 wt%, Mn: 1.0 wt% or less, P: 0.025 wt% or less, S: 0.035 wt% or less, Cu: 0.3 wt% or less, Cr: more than 4.0 to 6.0 wt%, Al: 0.05 wt% or less, O: 0.0015 wt% or less, N: 0.030 wt% or less, Ti: 0.005 wt% or less After quenching and tempering a part made of steel that has been spheroidized from the steel containing Fe and the inevitable impurities, the amount of solute C in the matrix excluding undissolved carbide of the part is 0.40. A power transmission component that transmits power by a frictional force having good contact fatigue characteristics, characterized by having a super-0.65 wt% hardness of the component being Hv 700 or higher. In Claim 4, it is further characterized by containing 1 type and 2 types of Ni: 1.0% or less, Mo: 1.0% or less, and the remainder which consists of Fe and an unavoidable impurity Power transmission component that transmits power by frictional force with excellent contact fatigue characteristics. 6. The power transmission component according to claim 4 or 5, wherein, for quenching and tempering, high-frequency induction heating is used and power is transmitted by a frictional force having good contact fatigue characteristics.

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