JPH0810826A - Production of cold drawn wire rod of alloyed steel for bearing - Google Patents

Abstract

PURPOSE:To produce a cold drawn wire rod of high quality alloy steel for bearing without developing abnormal spots at the time of trying heating with a simplified producing process. CONSTITUTION:The alloy steel rolled material rolled with the alloyed steel rolling stock for bearing containing 0.025-0.045-wt.% Al and 0.015-0.025wt.% N in an alloyed steel for machine structural use is annealed to disperse AlN and thereafter, pickling and coating treatment are executed. Successively, the finish wire-drawing having 20-35% reduction of area by the cold drawing and a flaw detecting test are executed and the cold drawn wire rod of the high quality alloyed steel for bearing without developing the abnormal spots at the time of treating the heating is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention produces an alloy steel cold drawn wire rod for bearings used as a material for rolling elements such as balls and rollers (straight rollers, tapered rollers, etc.) which are bearing elements. The present invention relates to a method for manufacturing a cold-drawn wire rod of alloy steel suitable for bearings.

[0002]

2. Description of the Related Art As a material for rolling elements such as balls and rollers, which are bearing elements, there is a high carbon chrome bearing steel material (SUJ 1-5) established in JIS G4805.

In such bearing steel, the C content is 0.9.
The content is considerably high at 5 to 1.10% by weight, and after heat treatment, not only the outer surface but also the interior has a large hardness.

On the other hand, there is an alloy steel for bearings which has a small internal hardness to ensure toughness, and whose surface is secured to a high hardness by a surface hardening treatment such as carburizing.

This alloy steel for bearings has a C content of 0.1.
The content is 5 to 0.40% by weight, which is less than that of the bearing steel such as SUJ2. For example, chrome steel materials (SCr415, SCr420, SCr43).
5, SAE5120, etc.) and chrome molybdenum steel (SCM415, SCM418, SCM420, SCM)
421, SCM435, SCM822, SAE4137
Etc.) and nickel chrome molybdenum steel materials (SNCM2
20, SNCM415, SNCM420, SNCM81
5, SAE 4320, SAE 8620, etc.), and roughly, C: 0.15 to 0.4
0 wt%, Si: 0.35 wt% or less, Mn: 1.20
Weight percent or less, Ni: 5.0 weight percent or less, Cr: 5.0 weight percent or less, Mo: 1.0 weight percent or less, and other appropriate alloying elements are used.

[0006] Conventionally, when manufacturing alloy steel wire rods for bearings used as raw materials for rolling elements such as balls and rollers constituting a bearing, the above chromium steel steel material, chromium molybdenum steel steel material, and nickel chromium molybdenum steel material are used. After pickling and coating a rolled alloy steel for bearings made of steel for machine structural use made of steel, etc., it is subjected to wire drawing and eddy current flaw detection tests by cold drawing, followed by annealing. A second pickling / coating treatment was performed, and subsequently, a second drawing wire drawing by cold drawing was carried out to obtain an alloy steel cold drawn wire rod for bearing.

[0007]

However, in the manufacturing process of such a conventional alloy steel cold drawn wire rod for bearings, there are two wire drawing steps, and therefore, two pickling / coating steps before wire drawing are required. Therefore, there is a problem that the number of processes is large, the amount of work in process increases during the process, and the manufacturing cost rises. Therefore, such alloy steel cold drawn wire rods for bearings are manufactured. There was a problem in that it was desired to shorten the process, reduce the amount of work in process during the process, and reduce the manufacturing cost. If an attempt is made to reduce the number of steps by a simple method, abnormal spots are likely to occur. Therefore, preventing the occurrence of such abnormal spots has also been a problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is a bearing element such as a ball,
When manufacturing alloy steel cold drawn wire rods for bearings used as materials for rolling elements such as rollers, even when the wire drawing process is performed only once, abnormal spots are observed during the subsequent heat treatment such as carburizing treatment. It is possible to produce high-quality alloy steel cold drawn wire rods for bearings that can be prevented from occurring and are not inferior in quality compared to the case where the conventional wire drawing process is performed twice. Since it is possible to perform the wire drawing process only once, the pickling / coating process before wire drawing can be done only once, which shortens the process and reduces the amount of work in progress during the process. The object of the present invention is to provide a method for manufacturing alloy steel cold drawn wire rods for bearings, which is capable of reducing manufacturing costs.

[0009]

A method of manufacturing alloy steel cold drawn wire rods for bearings according to the present invention is a method for manufacturing alloy steel for machine structure in which Al: 0.025 to 0.045% by weight, N: 0. 0
A rolled alloy steel for bearings, which is obtained by rolling an alloy steel material for bearings containing 15 to 0.025% by weight, is annealed to disperse AlN, followed by pickling and coating treatment, followed by cold drawing. The surface drawing ratio is 20 to 35%, and the finish wire drawing and flaw detection test are performed only once to obtain the alloy steel cold drawn wire rod for bearing having hardness of HRB90 to 98. .

In the embodiment of the method for manufacturing the alloy steel cold drawn wire rod for bearing according to the present invention, the alloy steel material for bearing is alloy steel for machine structure (SCr420, SCM).
420, SCr435, SCM435, SAE432
0, SAE5120, etc.), Al: 0.025 to 0.0
45% by weight and N: 0.015 to 0.025% by weight can be contained, and more specifically, for example, C:
0.15-0.40 wt%, Si: 0.35 wt% or less, Mn: 1.20 wt% or less, Ni: 5.0 wt% or less, Cr: 5.0 wt% or less, Mo: 1. The above Al and N may be added to the alloy containing 0% by weight or less and other appropriate alloy elements.

In the embodiment of the present invention, the annealing may be performed at 700 to 800 ° C. so as to uniformly disperse AlN in the rolled material, and the heating may be performed during the subsequent carburizing treatment. By preventing the occurrence of abnormal spots due to the pinning effect due to such fine dispersion of AlN, and by preventing the occurrence of abnormal spots, it is possible to reduce the heat treatment strain during carburizing and quenching, and prevent the fatigue strength and impact strength from decreasing. It is desirable to prevent deterioration of machinability.

Then, after such annealing, pickling / coating treatment, followed by finish drawing by cold drawing work, the area reduction ratio is set in the range of 20 to 35%, and the flaw detection test is performed. For example, by adopting the eddy current flaw detection test and performing the eddy current flaw detection test with a probe positioned between the cold drawing die and the wire rod steady roller, the alloy steel cold drawn wire rod for bearing Hardness of HRB90-98,
It is desirable to obtain a cold-drawn wire rod of alloy steel for bearings whose length is guaranteed to have a surface flaw of 0.05 mm or less.

FIG. 1 shows an embodiment of a method for producing a cold-drawn alloy steel wire for bearing according to the present invention. More preferably, the rolling dimension tolerance is ± 0. After forming a rolled alloy steel for bearings made of a precision rolled material of 15 mm, the rolled alloy steel for bearings is annealed at a temperature of 700 to 800 ° C. in the annealing step of step D2. This annealing is a treatment for softening the rolled material and uniformly dispersing AlN.
By obtaining the pinning effect by 1N, generation of abnormal spots is prevented at the time of subsequent heating for surface hardening heat treatment such as carburizing and quenching.

Then, after annealing, after pickling and coating treatment in the pickling / coating step of step D3, step D
In the finish wire drawing / flaw detection test process of 4, the finish wire drawing is performed only once and the flaw detection test is performed.

In this finish wire drawing and flaw detection test process, as shown in FIG. 2, the finish wire drawing by the cold drawing die 2 for the coated wire rod 1 reduces the surface area from the viewpoint of preventing the occurrence of abnormal spots. The ratio is preferably 20 to 35%, more preferably 25 to 30% to prevent the occurrence of abnormal spots. On the other hand, from the viewpoint of product hardness, it is 25 to 35%. It is good to set it as%.

This abnormal spot is a phenomenon that the crystal grains are locally coarsened during heating by heat treatment, and increase in heat treatment strain during carburizing and quenching (generation of cracks during strain correction), decrease in fatigue strength and impact strength, Although it causes machinability to deteriorate, in the present invention, the Al content in the machine structural alloy steel is 0.025 to 0.045 wt% and the N content is 0.0.
A nitride mainly composed of AlN is finely dispersed in an amount of 15 to 0.025% by weight, and an abnormal spot is prevented by obtaining a pinning effect of crystal grains by the fine dispersion.

Further, the area reduction rate in cold drawing is 20%.
The occurrence of abnormal spots is also prevented by optimizing the value to ˜35%.

In the flaw detection test, an eddy current flaw detection test can be used. In this case, as shown in FIG. 2, the probe 3 used in the eddy current flaw detection test is a cold drawing die 2 and this die 2. It is desirable to locate it between the wire rod steady rest roller 4 provided in the vicinity.

In this way, the product hardness is HRB90-
98, alloy steel cold drawn wire rods for bearings having a surface flaw of 0.05 mm or less can be obtained. For example, such a wire rod is cut into a predetermined length, and the cut pieces are used as a raw material for bearing processing by header processing or the like. It is formed into a roller for use.

[0020]

According to the method of manufacturing the alloy steel cold drawn wire rod for bearing according to the present invention, the alloy steel for machine structure is made of Al:
0.025-0.045% by weight, N: 0.015-0.
After rolling the alloy steel for bearings obtained by rolling the alloy steel for bearings containing 025% by weight to disperse AlN,
After pickling / coating, cold drawing process is applied to finish wire drawing with 20-35% reduction in area and flaw detection test, and alloy steel cold drawing wire for bearing with hardness of HRB90-98. Therefore, even when the wire drawing process is performed only once, the occurrence of abnormal spots during heating such as carburizing and quenching is prevented, and the conventional wire drawing process is performed twice. Since a high-quality alloy steel for cold-drawing wire rod for bearing, which is not inferior in quality to the case of manufacturing, will be manufactured, the wire-drawing process can be performed only once, and therefore, before the wire-drawing. Since the pickling / coating process only needs to be done once, the process can be shortened and the amount of work in progress in the intermediate process can be reduced.
This will result in a reduction in manufacturing costs.

Further, in the finish wire drawing by cold drawing, the area reduction ratio is set to be in the range of 20 to 35%.
Bearing alloy steel after manufacturing cold drawn wire rods are HRB90-9
8 having an appropriate hardness can be obtained, and the life of the working die can be favorably maintained when header processing or the like is performed to form the bearing element.

In addition, the flaw detection test is an eddy current flaw detection test, and the eddy current flaw detection test is performed by a probe positioned between the cold drawing die and the wire rod steadying roller to obtain, for example, hardness. Is HRB90 to 98, the surface flaw is 0.05 mm or less, and the alloy steel cold drawn wire rod for bearings with a guaranteed full length can be obtained.

[0023]

EXAMPLES Inventive Examples, Comparative Examples Rolled material having a diameter of 8.0 mm made of alloy steel for bearings (steel types A, B, C, D) having the chemical composition shown in Table 1 was obtained by wire rolling, and then Annealing was performed under the annealing conditions shown in Table 2 (in the case of the invention example) and Table 3 (in the case of the comparative example).

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

Next, after the annealing, a pickling treatment is carried out and then a coating treatment is carried out, and subsequently, passing through a die for cold drawing and finishing wire drawing by cold drawing are also shown in Table 2 and Table 3.
An eddy current flaw detection test was carried out with a probe arranged between the die and the steady rest roller to obtain the alloy steel cold drawn wire rod for bearing.

The hardness of the alloy steel cold drawn wire rod for bearing thus obtained was examined, and in the case of the present invention example,
As shown in Table 2, the alloy steels were prepared within the range of HRB 90 to 98, and were alloy steel cold drawn wire rods for bearings suitable for header processing. Further, the surface flaw was guaranteed to be 0.05 mm or less by the eddy current flaw detection.

On the other hand, in the case of the comparative example, as shown in Table 3, the hardness of the alloy steel cold drawn wire rod for bearing has the hardness of HRB90.
Some did not satisfy ~ 98 (the abnormal spots will be described later).

Conventional Example A rolled material made of alloy steel for bearings having the chemical composition shown in Table 1 and having a diameter of 8.00 mm was obtained by wire rolling, and then subjected to pickling treatment and coating treatment, and then shown in Table 4. Cold drawing after rolling was performed at a reduction in area, an eddy current flaw detection test was performed, and annealing was also performed under the annealing conditions shown in Table 4.

[0031]

[Table 4]

Next, the annealed wire is subjected to pickling treatment and coating treatment, and then cold drawn after annealing at the area reduction ratio shown in Table 4 as well to cold-roll alloy steel for bearings. A drawn wire rod was obtained.

The hardness of the alloy steel cold drawn wire rod for bearing thus obtained was examined, and as shown in Table 4, H
It is a complete set within the range of RB90-98,
Although the alloy steel for bearings was suitable for header processing, it was a cold drawn wire rod, but since it was drawn twice, it was necessary to perform pickling and coating treatment before drawing twice. .

Abnormal Spot Generation Test Next, the alloy steel cold drawn wire rods for bearings of the invention example, comparative example and conventional example thus obtained were cut to a required length, and
When the degree of occurrence of abnormal spots was examined by performing heat treatment of 70 ° C. × 6H → 900 ° C. × 30 min → oil cooling, Table 2
The results are shown in Table 3 and Table 4.

As shown in Table 2, in the case of the examples of the present invention in which the alloy steels contained appropriate amounts of Al and N and the area reduction ratio was optimized by cold drawing, the occurrence of abnormal spots was observed. I couldn't do it.

On the other hand, as shown in Table 3, even if an appropriate amount of Al and N is contained in the alloy steel, the area reduction rate during cold drawing is not appropriate, Abnormal spots were observed when N was not contained in an appropriate amount.

Further, as shown in Table 4, even in the case of the conventional example, the occurrence of abnormal spots is not recognized, but wire drawing by cold drawing is required at least twice, and therefore, at least twice. Since pickling and coating treatment are required, there are many steps, and the amount of work in progress increases during the steps, making it difficult to reduce the manufacturing cost.

[0038]

EFFECT OF THE INVENTION In the method for manufacturing the alloy steel cold drawn wire rod for bearing according to the present invention, the alloy steel for machine structure is made of Al:
0.025-0.045% by weight, N: 0.015-0.
After rolling the alloy steel for bearings containing 025 wt%, the rolled alloy steel for bearings is annealed to disperse AlN, followed by pickling and coating treatment, and subsequently, the area reduction ratio by cold drawing is 2
Since a finish wire drawing and flaw detection test of 0 to 35% were performed to obtain alloy steel cold drawn wire rods for bearings having hardness of HRB90 to 98, rolling elements such as balls and rollers, which are bearing elements, were obtained. When manufacturing alloy steel cold drawn wire rods for bearings used as a raw material, even when the wire drawing process is performed only once, it is possible to prevent the occurrence of abnormal spots during the subsequent heat treatment such as carburizing treatment. It is possible to manufacture a high quality alloy steel cold drawn wire rod for bearing which is not inferior in quality to the case where the conventional wire drawing process is performed twice. Since it is possible to complete the wire drawing process only once, it is possible to complete the pickling / coating process before wire drawing only once, which leads to shortening of the process and reduction of handling defects. Further improvement of lead time Condensation, reduction of in-process amount in the intermediate step, is remarkably excellent effect that the reduction of production cost can be realized resulting.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an embodiment of a method for producing a cold drawn alloy steel wire for bearing according to the present invention.

FIG. 2 is an explanatory view showing a positional relationship between a die, a flaw detection test probe, and a wire rod steadying roller in an embodiment of the method for manufacturing the alloy steel cold drawn wire rod for bearing according to the present invention.

Claims (4)

[Claims] 1. An alloy steel for machine structure, containing Al: 0.025
~ 0.045% by weight, N: 0.015 to 0.025% by weight, the rolled alloy steel for bearing is rolled to anneal the rolled alloy steel for bearing to disperse AlN, followed by pickling / coating treatment. Then, the area reduction rate by cold drawing is 20-35%.
After finishing wire drawing and flaw detection test, the hardness is HRB90.
~ 98 alloy steel cold drawn wire rod for bearings, wherein the alloy steel cold drawn wire rod for bearings is manufactured. 2. Annealing is performed at 700 to 800 ° C. to obtain AlN.
The method for producing the alloy steel cold drawn wire rod for bearing according to claim 1, which is a treatment for dispersing the alloy. 3. The eddy-current flaw detection test is an eddy-current flaw-detection test, and the eddy-current flaw detection test is performed by a probe positioned between the cold drawing die and the wire rod steadying roller.
A method for manufacturing the alloy steel cold drawn wire rod for bearings according to. 4. The method for producing an alloy steel cold drawn wire rod according to claim 1, wherein the surface flaw of the alloy steel cold drawn wire rod for bearing is 0.05 mm or less.