JPH10265850A - Production of straight motion support bearing member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the straight motion support bearing member without lowering a high frequency hardening property by reducing a number of processes consisting of drawing with an irregular shaped die and high frequency hardening in which drawings of three times or more and annealings of two times or more are heretofore executed. SOLUTION: In a production method of the straight motion support bearing member in which a high frequency hardened material is subjected to one time drawing with an irregular shaped die, after intermediate annealing, finish drawing and then high frequency hardening, a high frequency hardened steel, which has a composition consisting of, by weight, 0.36-0.70% C, 0.05-0.15% Si, 0.60-2.00% Mn, 0.01-0.20% Ti, <0.01% N, 0.0005-0.0050% B and the balance Fe with inevitable impurities, after hot rolling as pretreatment prior to drawing, is subjected to spheroidizing annealing at the Ac1 point to 800 deg.C as a max temp. succeeded by slow cooling to a hardness of <=85HRB, deformation resistance at cold drawing is reduced. It is seen from the hardness shown in a diagram that the austenized straight motion support bearing member is produced in a very short time under a temp. condition in the diagram.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a linear motion bearing member manufactured by drawing with a deformed die and induction hardening.

[0002]

2. Description of the Related Art Conventionally, a linear bearing member manufactured by induction hardening after drawing by a deformed die is made of medium carbon steel, subjected to spheroidizing annealing after rolling, and subjected to at least three times of drawing and at least two times of drawing. It was manufactured by performing induction hardening after annealing. However, if a steel member used for a conventional linear motion bearing member is used after being spheroidized and annealed, deformation resistance at the time of drawing is large. Therefore, it is necessary to repeat drawing and annealing at least three times or more. There was a disadvantage that the process cost was high.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a process for manufacturing a linear motion bearing member which has been manufactured by drawing and induction hardening using a deformed die, which has conventionally been drawn three times or more and annealed twice or more. It is an object of the present invention to provide a method for producing a linear motion bearing member through an induction hardening step after two extractions and one intermediate annealing including a finish extraction without lowering the induction hardening property without reducing the induction hardening property.

[0004]

SUMMARY OF THE INVENTION The present invention provides a conventional induction hardened steel in which the components are changed to satisfy the hardenability and to improve the cold workability to reduce the deformation resistance at the time of working. It is. And the means use induction hardening material,
In a method of manufacturing a linear motion bearing member which performs one drawing with a deformed die, performs intermediate annealing, finishes drawing, and then manufactures through an induction hardening process, the component of the induction hardened material is expressed as C: 0.36-0.7
0%, Si: 0.05 to 0.15%, Mn: 0.60 to
2.00%, Ti: 0.01 to 0.20%, N: <0.
01%, B: 0.0005 to 0.0050%, balance Fe
And a steel having a composition consisting of unavoidable impurities. After hot rolling as a treatment before drawing, the highest point temperature is set from A _C1 point to 800 ° C., and then spheroidizing annealing is performed by slow cooling, and the hardness is 85H.
RB or less to reduce the deformation resistance during cold drawing, so the direct-acting bearing member conventionally manufactured by three times of drawing is manufactured by one drawing and two times of finish drawing after intermediate annealing. It is possible to do.

The reasons for limiting the chemical components of the induction hardened steel will be described below. C requires the surface hardness of the direct-acting bearing member, but if it is less than 0.36%, the hardness after induction hardening cannot be secured, and if it exceeds 0.70%, the cold workability deteriorates. Therefore, C is set to 0.36 to 0.70%.

Mn is an element that improves induction hardenability, but if it is less than 0.60%, induction hardenability is not sufficient, and if it exceeds 2.00%, cold workability is reduced. Therefore, Mn is set to 0.60 to 2.00%.

[0007] If Si is less than 0.05%, the deoxidizing effect is not sufficient, and if it exceeds 0.15%, the ferrite hardness increases, and the cold workability decreases. Therefore, Si is set to 0.
It is set to be from 0.05 to 0.15%.

[0008] If free N is present in the steel, Ti forms BN and solid solution B disappears, so that N is fixed by Ti. That is, N forms a nitride with N to reduce solid solution N in ferrite, thereby reducing deformation resistance during cold working, and improving the effect of B on hardenability. If it is less than 0.01%, it is insufficient to fix N, and if it exceeds 0.20%, the cold workability is reduced. Therefore, Ti is 0.01 to 0.20
%.

[0009] When N is contained in an amount of 0.01% or more, TiN increases, and the rolling fatigue life is adversely affected. Therefore, N is set to less than 0.01%.

[0010] B is an element which significantly improves the hardenability of steel by the addition of a trace amount, but if its content is less than 0.0005%, its effect is not sufficient. Lower. Therefore, B is 0.0005%
To 0.0050%.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The steel composition according to an embodiment of the present invention is shown in Examples of Table 1. The example corresponds to steel having a carbon content of S55C, and the example 1 corresponds to S55C.
In this case, Si and Mn are reduced, and B is added. Comparative Example 1 is a typical conventional steel, and Comparative Example 2 is one in which Mn is further reduced from the steel of Example. Using these steels, the hardness after annealing, the deformation resistance of cold drawing, and the induction hardening were evaluated, and a linear bearing was manufactured by drawing twice with intermediate annealing using a deformed die. Less than,
An embodiment of the present invention will be described further than an example.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Test steels (comparative examples 1, 2 and examples) having the chemical composition shown in Table 1 were melted in a 100 kg vacuum melting furnace, and heat treatment tests, cold workability tests, and high frequency A hardenability test was performed.

The heat-treated test piece is forged to 20 mmφ by hot forging, and a test piece of 15 mmφ × 100 mmL is prepared by cutting, and the highest point temperature is set to A ₁ point to 800 ° C. by an atmospheric furnace, and then gradually cooled. Spheroidizing annealing was performed, and the hardness after the heat treatment was examined. Table 2 shows the results. From Table 2, the hardness of the conventional steel does not become 85 HRB or less even when the spheroidizing annealing is performed at any highest point temperature, but the hardness of the Example and Comparative Example 2 becomes 85 HRB or less under any conditions.

[0014]

[Table 1]

[0015]

[Table 2]

Next, the cold workability test specimen is 20 m in hot forging.
After forging to mφ, spheroidizing annealing was performed at a maximum point temperature of 770 ° C. to form a cylindrical test piece of 14 mmφ × 21 mmH for an end-face constrained compression test, and the deformation resistance during cold working was measured. Table 3 shows the results. From the results, the example,
And the steel shown in Comparative Example 2 has significantly reduced deformation resistance during cold working as compared with the conventional steel of Comparative Example 1. In the case of the conventional three-time drawing, the first and second processing rates are about 20%. However, when the second-time drawing is performed, the processing rate is about 40%. However, 40% of the steel shown in the example subjected to spheroidizing annealing was used.
The deformation resistance at the time of% processing is smaller than the deformation resistance at the time of 20% processing of the conventional steel. For this reason, by using the steel shown in the examples, what could not be formed conventionally without drawing three or more times can be manufactured by drawing twice.

[0017]

[Table 3]

The induction hardenability test piece was forged to 30φ by hot forging, and was cut from its D / 4 position to obtain a 3 m
A test piece of mφ × 10 mmL is prepared, heated at a constant temperature for a predetermined time and then rapidly cooled to obtain a TTA (Time-Temperature).
-Austenizing) A test was performed to determine a diagram. The results are shown in FIGS. FIG. 1 shows a TTA diagram of the steel shown in the examples, and a hardness of 720 HV or more is used as a standard for austenitization. At this time, it can be seen from the hardness shown in the figure that under the temperature conditions in the figure, the austenite was completely formed even by heating for a very short time. FIG. 2 shows a TTA diagram of the steel shown in Comparative Example 1, and it can be seen that, under the temperature conditions in the diagram, as in FIG. .

FIG. 3 is a graph showing Mn according to the present invention.
FIG. 4 shows a TTA diagram of the steel of Comparative Example 2 having a low amount, but when the holding time is short at a heating temperature of 850 ° C. or less,
Normal hardness is not obtained, it does not completely austenite,
Ferrite remains. Also, there is a problem that an incompletely quenched phase appears even under the condition that no residual ferrite remains. In such a structure, the life of the linear motion bearing is significantly reduced.

Further, Table 4 shows the results of performing twice drawing with a deformed die using steel having the above characteristics. The steels shown in Examples and Comparative Example 2 having low deformation resistance during drawing can be formed by drawing twice. However, with the conventional steel shown in Comparative Example 1, there is a problem that a normal shape cannot be obtained after drawing, and the steel sometimes breaks during drawing.

[0021]

[Table 4]

From the above results, when the steels shown in Examples and Comparative Example 2 are used, a linear motion bearing member can be manufactured by a total of two times of drawing, one drawing with a deformed die and the finish drawing after intermediate annealing. However, when the steel of Comparative Example 2 is used, a uniform hardened structure cannot be obtained during induction hardening, and the life of the linear motion bearing may be significantly reduced.

[0023]

As described above, after the steel having the chemical composition according to the present invention is hot-rolled, the temperature between the AC ₁ point and 800 ° C. is set to the highest point temperature, and then the steel is subjected to spheroidizing annealing by slow cooling. By reducing the hardness to 85 HRB or less, the direct-acting bearing member, which has conventionally been manufactured by induction hardening through three times of drawing with a deformed die and two times of intermediate annealing, can reduce the hardness by 2 hours without deteriorating the induction hardenability. It can be manufactured by induction hardening only through one drawing and one intermediate annealing, and has an excellent effect that the number of steps and the process cost can be reduced.

[Brief description of the drawings]

FIG. 1 shows a TTA diagram of the chemical component composition shown in the examples. The hardness is measured for each holding time at each temperature, and the structure is observed by an optical microscope.
This shows the easiness of austenitization. The circles in the figure indicate measurement points, and the numerical values beside them indicate hardness (HV).

FIG. 2 shows a TTA diagram of the chemical composition shown in Comparative Example 1. The hardness was measured for each holding time at each temperature, and the structure was observed by an optical microscope to observe the structure of austenite. It shows ease. The circles in the figure indicate the measurement points, and the numerical values beside them are hardness (HV).
Is shown.

FIG. 3 shows a TTA diagram of the chemical composition shown in Comparative Example 2. The hardness was measured for each holding time at each temperature, and the structure of austenitized steel was observed by optical microscopy. It shows ease. The circles in the figure indicate the measurement points, and the numerical values beside them are hardness (HV).
Is shown.

Claims (1)

[Claims] (1) C: 0.36 to 0.70% by weight,
Si: 0.05 to 0.15%, Mn: 0.60 to 2.0
0%, Ti: 0.01 to 0.20%, N: <0.01
%, B: 0.0005 to 0.0050%, and after hot rolling a steel having a composition consisting of the balance of Fe and unavoidable impurities, A
_C1 point ~ 800 ℃ as the highest point temperature, then perform spheroidizing annealing by slow cooling, make the hardness less than 85HRB, perform one drawing with a deformed die, perform intermediate annealing, then perform finish drawing, Thereafter, induction hardening is performed.