JPH02209452A - Steel for rolling parts and rolling parts using the steel - Google Patents

Abstract

PURPOSE:To combinedly improve the workability and hardenability of the steel for rolling parts by reducing the contents of Mn and Si, adding Cr and Mo so as to compensate the hardenability and specifying the compsn. CONSTITUTION:The steel for rolling parts is constituted of, by weight, 0.1 to 0.7% C, <=0.04% Si, <=0.25% Mn, 0.2 to 1.0% Cr, <=0.8% Mo, <=0.01% P, <=0.003% S, <=0.0015% O and the balance Fe. In the steel, since S and O form inclusions deteriorating the deformability at the time of plastic working, each is regulated to the upper limit or below. Since Mn and Si increase the deformation resistance and deteriorate the plastic workability as well as Mn forms MnS with S as impurities and causes the generation of cracks, each is regulated to the upper limit or below. Then, the deterioration of the hardenability caused by the reduction of the contents of Mn and Si is compensated by the addition of Cr and Mo.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to steel for rolling parts such as rolling bearings used in automobiles, agricultural machinery, construction machinery, steel machinery, etc., and the steel for rolling parts. It relates to long-life rolling parts plastically worked using

[Conventional technology]

Conventionally, when manufacturing the inner and outer rings of rolling bearings such as rolling ball bearings and 9 spherical roller bearings using bearing steel (for example, JTSSUJ-2), cold rolling is used to manufacture cylindrical blanks. The conventional practice has been to cold-work the steel into a ring shape until turning after cold rolling becomes unnecessary, and then carburize and harden it.

The applicant of this application has proposed a rolling bearing that has excellent workability by preventing the occurrence of cranks during plastic working such as cold rolling and upsetting (Japanese Patent Application No. 63-27899).
No. 2).

[Problem to be solved by the invention]

However, even when conventional bearing steels are subjected to spheroidizing annealing treatment, they have problems such as low deformability during cold working, high deformation resistance, and insufficient isoplastic workability.

If the deformability during plastic working is low, the processing rate until cracking occurs will be low, and cracks or cracks will occur in areas with low deformability, which will become the starting point of the crank. When this crack occurs, it causes cracks in the inner and outer rings. Therefore, 0.4 to 0
．． 7 mm of extra thickness is added in advance, and since cranking occurs in this extra thickness, machining has been carried out to scrape off the extra thickness after machining is completed.

On the other hand, in order to omit such addition and deletion of extra thickness, it is necessary to perform processing at a certain degree of reduction in machining and then add turning processing to form the final shape.

In addition, if the deformation resistance during processing is high, a large forming load (
For example, in the case of cold rolling, the tool used for processing, such as the mandrel, may break early, reducing the tool life, and the processing speed cannot be increased, resulting in a long forming time. There was an issue.

On the other hand, for rolling parts, the required rolling fatigue life (hereinafter referred to as
In order to ensure the longevity of rolling parts, it is important to improve the hardenability of steel for rolling parts to obtain the necessary surface hardness.

Therefore, in order to solve the above-mentioned problems, the invention of this application has as its first object to provide a steel for rolling parts that has excellent workability and hardenability. The second object is to provide rolling parts that use steel and have a long life and can be manufactured at low cost.

[Means for Solving the Problem] In order to achieve the first object, the steel for rolling parts according to claim (1) contains C; 0.1 to 0.7% by weight, Si;
0.04% by weight or less, 0.25% by weight or less, Cr; 0.
2 to 1.0% by weight, Mo; 0.8% by weight or less, 0; 0.
0.015% by weight or less, the balance being Fe and unavoidable impurities.

Further, the steel for rolling parts according to claim (2), which also achieves the above first object, contains C; 0.1 to 0.7% by weight, S
i; 0.04% by weight or less, Mn; 0.25% by weight or less,
Cr; 0.2 to 1.0% by weight, TiHo, 0.5% by weight or less, Mo; 0.5% by weight or less, B; 0.0005 to 0
．． 003% by weight, N; 0.0 O5% by weight or less, P
; 0.01% by weight or less, S; 0.003% by weight or less, 0
; 0.0015% by weight or less, the balance being Fe and unavoidable impurities;
C: 0.1-0.7% by weight, Si: 0.04% by weight or less, Mn: 0.25% by weight or less, Cr: 0, 2-1.0
Weight%, Mo; o, 8% by weight or less, 0; 0, 0
The present invention is characterized in that a steel for rolling parts comprising 0.015% by weight or less, the balance being Fe and unavoidable impurities is plastically worked into a predetermined shape.

Similarly, the rolling component according to claim (4) which achieves the second object has C: 0.1 to 0.7% by weight, Sl: 0.
04% by weight or less, M n ; 0.25% by weight or less, C
r: 0.2-1.0% by weight, Ti: 0.05% by weight or less, Mo: 0.5% by weight or less, B, O, O005-0
．． 003% by weight, N; 0. 005% by weight or less, P
, 0.01% by weight or less, S; 0.003% by weight
Hereinafter, ○; 0.0015% or less, residual gravity e and unavoidable impurities, steel for rolling parts is plastically worked into a predetermined shape.

Further, the rolling component according to claim (5) that achieves the second object has Ci 0.1 to 0.7% by weight, Si;
0.04% by weight or less, Mn; 0.25% by weight or less, Cr
; 0.2 to 1.0% by weight, Mo; 0.8% by weight or less, 0
, 0.0015% by weight or less, the balance being Fe and unavoidable impurities, the steel for rolling parts is plastically worked into a predetermined shape,
It is characterized in that it is then subjected to hardening heat treatment.

Similarly, the rolling component according to claim (6), which achieves the second object, comprises C; 0.1 to 0.7% by weight, Si; 0.7% by weight.
04% by weight or less, Mn; 0.25% by weight or less, Cr; 0
．． 2 to 1.0% by weight, Ti; 0.05% by weight or less, M
o + 0.5% by weight or less, B, 0.0005-0
．． 0033 Juumaru, N i O, 005% by weight or less, P
; 0.01% by weight or less, S; 0.003% by weight or less, 0, 0.0015% by weight or less, the balance being Fe and unavoidable impurities. Steel for rolling parts is plastic worked into a predetermined shape, and then hardened. It is characterized by being heat treated.

[Effect]

The invention related to this application reduces the content of O19, which forms inclusions that reduce deformability during plastic working, and the content of Mn and St, which increase deformation resistance, and
, Cr,
This is attempted to be compensated for by including Mo or further B.

Next, the effects of the contained elements and the critical significance of their content will be explained.

C, 0.1 to 0.7% by weight When C is lower than 0.1% by weight, the carburizing or carbonitriding heat treatment time becomes long, and the heat treatment productivity decreases. Moreover, if the content exceeds 0.7% by weight, deformation resistance increases and plastic workability decreases. Therefore, from the above, c-1 was limited to within the range of the above values.

Si: 0.04% by weight or less Si is necessary as a deoxidizing agent during steel manufacturing and to improve hardenability, but if it is contained in excess of 0.04% by weight, it increases deformation resistance during high deformation. Therefore, the Si content was selected within the above value range.

Mn: 0.25% by weight or less Mn is an element necessary to improve hardenability,
By increasing the deformation resistance, the plastic workability is reduced, and at the same time, it combines with S, an impurity, to form MnS, which becomes a starting point for crack generation.

Therefore, the upper limit of the Mn content was set to 0.25% by weight.

In the present invention, the decrease in hardenability caused by the decrease in Si and Mn contents is compensated for by containing Cr, Mo, and B.

Cr; 0.2 to 1.0% by weight Cr is an element necessary to improve hardenability by compensating for the decrease in hardenability due to low Si and low Mn, and to further improve wear resistance. If the content is less than 0.2% by weight, the hardenability and wear resistance will be insufficient, and if the content exceeds 1.0% by weight, a large amount of Cr carbide will be produced, which will actually shorten the service life. Therefore, the content was selected within the above range.

Mo: 0.8% by weight or less (Claims (1), (3),
(5) Invention) 0.5% by weight or less (Claims (2), (4), (6)
Description of the Invention) Like Cr, Mo is an element necessary to improve hardenability by compensating for the decrease in hardenability due to low Si and low Mn. However, since there is no difference in the effect even if the content exceeds 0.8% by weight, in the invention described in claims (1), (3), and (5), the upper limit of the content is set to 0.8% by weight. did.

In the inventions described in claims (2L (4) and (6)), B is further contained to compensate for the decrease in hardenability due to low St and low Mn, but when B is contained, MO is 0. 5
Since there is no difference in the effect of improving hardenability even if the content exceeds 0.5% by weight, the upper limit of the content is set to 0.5% by weight.

B, 0. O005~0.003wt%B is low St
Since this element is necessary to compensate for the decrease in hardenability caused by low Mn, the lower limit of the content is set to 0.0005% by weight.
B1. 'j-1-.

On the other hand, 0. If OO is contained in an amount exceeding 3% by weight, it will precipitate at grain boundaries and cause grain boundary embrittlement, so claims (2) and (4)
, In the invention described in (6), the upper limit of the content of B is 0.00.
It was bound at 3% by weight.

Ti: 0.05% by weight or less Ti is an element necessary to fix N, which is an impurity, as TiN. N reacts with B to form BN, which inhibits the effect of B on improving hardenability. Therefore, Ti is added to fix N and ensure necessary hardenability. Therefore, Ti was added to the inventions described in claims (2) and (4L (6)) containing B. It also becomes TiN, which makes the crystal grains finer and has the effect of extending the life of rolling parts. be.

However, a content of 0.05% by weight is sufficient, and if the amount added is too large, carbides are generated, causing a decrease in toughness, so the upper limit of the content was selected as the above value.

N: 0.005% by weight or less N is an impurity contained in steel, and its amount must be reduced as much as possible. N reacts with B to form BN, which inhibits the hardenability improvement effect of B.

In addition, although Ti is contained in the inventions described in claims (2L (4) and (6)), Ti produced by the addition of Ti
Since N causes a decrease in life and also causes age hardening due to temperature rise during plastic working, which is accompanied by an increase in deformation resistance, in the inventions described in claims (2), (4), and (6), the N content is The upper limit of is selected to be the above value.

P, 0.01% by weight or less P, like N, is an impurity contained in steel, and its content must be reduced as much as possible. The upper limit was selected to be the above value because P causes age hardening due to temperature rise during plastic working, which is accompanied by an increase in deformation resistance and reduces plastic workability.

S, 0.003% by weight or less S is an impurity that causes the formation of sulfide-based nonmetallic inclusions such as MnS. MnS has low hardness and deformability,
Acts as a starting point for crank generation during plastic working such as cold rolling. Therefore, in order to prevent cracking during plastic working of rolling parts and enable stronger working, it is necessary to lower the S content, and the upper limit is set at 0. OO was set to less than 3%.

0; O; 0.0015% by weight or less 0 is an oxide-based nonmetallic inclusion-generating element that reduces deformability and shortens the life of rolling parts, so it is necessary to reduce its content as much as possible. Therefore, the upper limit of the content was set to 0.
The content was selected to be 0.0015% by weight.

In the invention described in claim (1), the content of Si, Mn, and P, which increase deformation resistance during plastic working, is reduced, and the content of S, 0, which inhibits deformability during plastic working, is reduced. are doing. The decrease in hardenability due to the reduction in St and Mn contents is compensated for by adding Mo and Cr.

As a result, it is possible to provide steel for rolling parts with improved plastic workability and hardenability.

In the invention described in claim (2), the contents of St, Mn, P, and N are reduced to reduce deformation resistance during plastic working. Furthermore, the content of S and 0, which inhibit deformability during plastic working, is reduced.

The decrease in hardenability due to the reduction of Si and Mn contents is
This is compensated by adding o, Cr, and B.

As a result, similar to the steel for rolling parts according to claim (1),
Steel for rolling parts with improved cold workability and hardenability can be provided.

In the invention described in claim (3), a rolling part is provided by subjecting the steel for rolling parts according to claim (1) to plastic working.

As a result of the excellent plastic workability of the steel for rolling parts according to claim (1), it is possible to perform plastic working with no cracks and higher working strength, and to that extent, it is possible to perform rolling parts with a long service life equivalent to that of the conventional steel. We can provide moving parts.

Furthermore, since the steel for rolling parts according to claim (1) has excellent plastic workability, it is possible to improve the life of the tool for plastic working and shorten the forming time based on the improvement of the processing speed. Based on the fact that the processing strength can be increased, the turning process after plastic working can be reduced, and since plastic working can be performed to the final shape, the material yield can be improved, making it possible to reduce the cost of rolling. We can provide parts.

In the invention as claimed in claim (4), the steel for rolling parts as claimed in claim (2) which has excellent plastic workability is subjected to plastic working to provide rolling parts. ), it is possible to provide rolling parts that have the same long life as conventional ones and are low in cost.

In the invention of claim (5), the steel for rolling parts according to claim (1), which has excellent not only plastic workability but also hardenability, is subjected to plastic working and is further subjected to hardening heat treatment. , it is possible to secure the higher hardness required for rolling parts that do not undergo hardening heat treatment through plastic working alone.
Longer life compared to the rolling parts according to claim (3),
In addition, it is possible to provide a low-cost rolling component similar to the rolling component described in claim (3).

In the invention of claim (6), the rolling parts are made by subjecting the steel for rolling parts having excellent plastic workability and hardenability according to claim (2) to plastic working, and in addition, hardening heat treatment. Claim (4) has a longer life compared to the rolling parts described in steel, and is low in cost like the rolling parts described in claim (4). It is possible to provide rolling parts.

〔Example〕

Next, examples of the present invention will be described.

Example steels (Al to A7) and comparison side meshes (Bl to B4) having the compositions shown in Table 1 below were melted in a 100 kgf vacuum melting furnace and subjected to spheroidizing annealing for 1 hour. After further forging to φ50, the steel listed in Table 1 is turned into a predetermined blank shape, and then formed by cold rolling without constraining the inner ring of a single-row deep groove ball bearing and the outer diameter of the shaft. I did it.

(Hereinafter, blank space) Fig. 1 shows a half cross section of the inner ring and the outer ring in the thickness direction. FIG. 1 (1) shows a cylindrical blank before cold rolling of the outer ring, and FIG. 1 (2) shows an outer ring obtained by cold rolling this cylindrical blank. (
1) In the figure, d is the outer ring radius before cold rolling, and (2) in the figure, d2 is the outer ring radius after cold rolling. Furthermore, in Figure (2), numeral 1 indicates a deep groove on the outer ring side formed as a result of cold rolling.

Further, FIG. 1(3) shows a cylindrical blank before cold rolling of the inner ring, and FIG. 1(4) shows an inner ring obtained by cold rolling this cylindrical blank.

In the figure (3), dl is the radius of the inner ring before cold rolling, and in the figure (4), d2 is the radius of the inner ring after cold rolling. Moreover, in FIG. (4), 2 is a groove on the inner ring side formed as a result of cold rolling.

In FIG. 1, the radius of the blank before cold rolling (d
l) and the radius (d2) of the molded product after cold rolling (dz
/dt) is the rolling ratio, and the larger this ratio is, the greater the working strength in cold rolling is.

In this example, the rolling ratio was selected to be 1.6 and cold working was performed.

Each of the Example steel and Comparative Example steel listed in Table 1 was cold-worked, and the forming pressure, forming time, and mandrel life when manufacturing the inner ring and outer ring of a single row ball bearing were measured. The results are shown in Table 2 below.

(Hereinafter, blank space) Table 2 In Table 2, forming load means the pressing force of the mandrel that presses into contact with the molded object, and forming time means the time required to manufacture one of the molded objects. The mandrel life is expressed as the number of molded bodies that can be rolled until the mandrel wears out to a certain level.

As can be seen from Tables 1 and 2, in comparative steel 82B4,
Since the contents of Si and Mn are both outside the scope of the present invention,
Deformation resistance increases. As a result, a large forming load and a long forming time are required, the life of the tool (mandrel) is greatly reduced, and the manufacturing efficiency of the inner and outer rings is also reduced.

In addition, in comparative example steels BL and B3, Si or M
Only the content of n is outside the scope of the present invention, but it causes the same problem as above.

On the other hand, in the example steel, St
, since the content of Mn is low, plastic workability is good, making it possible to form with a small load and in a short time, greatly improving tool life and improving the manufacturing efficiency of inner and outer rings. . As a result, by manufacturing rolled parts using the steel of the present invention, it becomes possible to provide rolled parts with high manufacturing efficiency and at low cost.

Furthermore, since the forming load is reduced, it becomes possible to cold-roll rings with even smaller inner diameters.

On the other hand, when each of the example steels was visually inspected for the occurrence of cranks at the inner diameter of the inner ring or outer ring (3 in Figure 1) during cold rolling, cracks were observed in all cases. There wasn't. This reduces the deformability of O1
This is because the content of 9 is small. Therefore,
Apply strong plastic working (in this example, the rolling ratio is 1.
6) can be performed, and the life of the rolled parts can be improved. Moreover, as a result of being able to increase the working strength, it is possible to perform plastic working to the final shape without requiring turning after working, and it is possible to realize cost reduction.

Next, a single row deep groove ball bearing was completed using the cold rolled formed rings (inner ring, outer ring), and the wear resistance and rolling fatigue resistance during use of the bearing were determined according to the conditions shown in Table 3. Hardening and quenching heat treatment was performed to impart When the C content is low (0.45% by weight or less), quenching is performed after carburizing (carbonitriding is also possible), and when the C content exceeds 0.45% by weight, normal quenching is performed. .

Among the heat treatments shown in Table 3, carburizing heat treatment is R,
Approximately 3 hours at 930″C in an atmosphere of enriched gas.
Heat treated at ±5°C, then oil quenched, and further heated to 160°C.
Tempering was carried out at °C for 2 hours.

Then, the surface hardness of the heat-treated rolling bearings was measured, and the surface hardness of the rolling bearings was measured as well.
A rolling life test (indicated by L+o) was conducted using the testing machine described on pages 21 to 21j.

The test conditions are as follows.

Radial load (F r) = 1400kg-fN = 4
00Or, p, m Lubricant oil #68 Turbine oil bath The results are shown in Table 3 below.

As can be seen from Table 3, the Example steel has a life equal to or longer than the Comparative Example steel, even when compared with the Comparative Example steel.

This means that the decrease in hardenability caused by the reduction in the contents of Mn and Si can be sufficiently compensated for by adding Mo and CrB. Therefore, Mn, S
It can be confirmed that even if the content of i is reduced, good hardenability can be ensured, and as a result, it is possible to provide a rolling bearing with a long life.

In the embodiments described above, a rolling bearing manufactured by cold rolling was described as a rolling component, but the rolling bearing is not limited thereto, and can be manufactured using other plastic working methods. The present invention can be applied to other rolling parts.

Examples of such rolling parts include tapered roller bearings manufactured by cold forging, and rolling parts such as rollers and balls.

Furthermore, in the above embodiments, carburizing and quenching and oil quenching have been described as hardening heat treatments, but the present invention is not limited thereto and may be other quenching heat treatments.

It is also possible to harden rolling parts using induction hardening, flame hardening, or the like.

〔Effect of the invention〕

As explained above, according to the invention described in claims (1) and (2), the content of St and Mn, which reduce plastic workability, is reduced, and elements that improve hardenability are added, and Si ,
Since the decrease in hardenability due to the reduction in Mn is compensated for, it is possible to provide a steel for rolling parts that is excellent in both hardenability and plastic workability.

Further, according to the invention described in claims (3) and (4), rolling parts can be obtained by plastic working the steels for rolling parts of claim (11(2)) each having excellent plastic workability. Therefore, it is possible to provide rolling parts with the same long life as conventional products and at low cost.

Furthermore, according to the invention described in claims (5) and (6),
Claim (1), which has excellent plastic workability and hardenability;
Since the rolling parts are obtained by further applying hardening heat treatment to each of the steels for rolling parts in (2) after plastic working, it is possible to secure higher hardness required for rolling parts. It is possible to provide a rolling component that has a longer lifespan than the rolling components of claims (3) and (4) and is also low-cost like the rolling components of claims (3) and (4).

[Brief explanation of the drawing]

FIG. 1 is a half-sectional view in the thickness direction of an inner ring and an outer ring before and after cold rolling.

Claims (6)

[Claims] (1) C: 0.1-0.7% by weight, Si: 0.04% by weight or less, Mn: 0.25% by weight or less, Cr: 0.2-1
．． 0% by weight, Mo: 0.8% by weight or less, P: 0.01% by weight or less, S: 0.003% by weight or less, O: 0.001
A steel for rolling parts, comprising 5% by weight or less, the balance being Fe and unavoidable impurities. (2) C: 0.1-0.7% by weight, Si: 0.04% by weight or less, Mn: 0.25% by weight or less, Cr: 0.2-1
．． 0% by weight, Ti: 0.05% by weight or less, Mo: 0.5
Weight% or less, B; 0.0005 to 0.003% by weight, N
; 0.005% by weight or less, P; 0.01% by weight or less, S
0.003% by weight or less; O; 0.0015% by weight or less; the balance being Fe and unavoidable impurities. (3) C: 0.1-0.7% by weight, Si: 0.04% by weight or less, Mn: 0.25% by weight or less, Cr: 0.2-1
．． 0% by weight, Mo: 0.8% by weight or less, P: 0.01% by weight or less, S: 0.003% by weight or less, O: 0.001
1. A rolling component comprising steel for a rolling component comprising 5% by weight or less, the remainder being Fe and unavoidable impurities, which is plastically worked into a predetermined shape. (4) C: 0.1-0.7% by weight, Si: 0.04% by weight or less, Mn: 0.25% by weight or less, Cr: 0.2-1
．． 0% by weight, Ti: 0.05% by weight or less, Mo: 0.5
Weight% or less, B; 0.0005 to 0.003% by weight, N
; 0.005% by weight or less, P; 0.01% by weight or less, S
0.003% by weight or less; O; 0.0015% by weight or less; the balance being Fe and unavoidable impurities. (5) C: 0.1-0.7% by weight, Si: 0.04% by weight or less, Mn: 0.25% by weight or less, Cr: 0.2-1
．． 0% by weight, Mo: 0.8% by weight or less, P: 0.01% by weight or less, S: 0.003% by weight or less, O: 0.001
A rolling component comprising steel for rolling components comprising 5% by weight or less, the balance being Fe and unavoidable impurities, which is plastically worked into a predetermined shape and then subjected to hardening heat treatment. (6) C: 0.1-0.7% by weight, Si: 0.04% by weight or less, Mn: 0.25% by weight or less, Cr: 0.2-1
．． 0% by weight, Ti: 0.05% by weight or less, Mo: 0.5
Weight% or less, B; 0.0005 to 0.003% by weight, N
; 0.005% by weight or less, P: 0.01% by weight or less, S
; 0.003% by weight or less; O; 0.0015% by weight or less; the balance being Fe and unavoidable impurities. rolling parts.