JP2006291239A - Method for producing high-carbon chromium bearing steel-forged rough-shaped material for inner and outer rings of general purpose small type bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving and mass-producing a bearing-race for hot-forging from a high carbon chromium bearing steel and the bearing race having the steel toughness, produced with the method. <P>SOLUTION: An annular body 2 having a center hole 3, is formed from a round bar of the high carbon chromium bearing steel by hot-forging with a horizonal type high speed forging apparatus, and the carbon content on the surface layer part is decarburized to ≤0.20% with a spheroidizing annealing, and an annular groove 7 is machined at the interval between the outer diameter surface 4 of the annular body 2 and the inner diameter surface 6 of the center hole 3 and formed into a double ring body 11 of an outer ring rough-shape 9 and an inner ring rough-shape 10 connected with the thin thickness part 8 to both shapes and successively, the thin thickness part 8 is punched out with pressing and the outer ring rough-shape 9 and the inner ring rough-shape 10 are fully separated. The inner diameter surface of the obtained outer-ring rough-shape 9 and the outer diameter surface of the inner-ring rough-shape 10, are machined and formed into raceway-tracking surfaces 12, 13 shown in the figure 2. The carbon in the raceway-tracking surfaces 12, 13 is 0.95-1.10% the original carbon content as SUJ2, and on the other hand, the carbon on the surface layer part of the raceway holding part, except the raceway-tracking surface is remained as the decarburized layer having ≤0.20% carbon content and formed as the outer-ring and the inner ring. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to the manufacture of inner and outer rings of a small general-purpose bearing having an outer ring outer diameter of φ26 to 41 mm made of a high carbon chrome bearing steel forged material.

  SUJ2 specified in JIS G 4805, a high-carbon chromium bearing steel used as a material for inner and outer rings of small-diameter general-purpose bearings, has been used for many years because of stable results such as good turning performance, ease of heat treatment, and rolling fatigue life. There is.

  Furthermore, in the manufacture of inner and outer rings for bearings, various manufacturing processes are employed to improve material yield and reduce the number of turning steps in order to reduce manufacturing costs. In particular, for inner and outer rings of small-diameter general-purpose bearings with an outer diameter of φ26 mm or more and φ41 mm or less, an annular body having a central hole is heated from a steel bar material with a horizontal high-speed forging device of 100 to 170 pieces per minute. Formed by hot forging, the formed annular body is forged into a spheroidized shape, and then integrally formed into inner and outer ring elements connected by a thin part by turning from this annular body. Many manufacturing methods are employed in which after parting and separating into inner and outer ring elements, finish turning to a predetermined bearing race shape is performed.

  By the way, as a manufacturing method of such bearing inner and outer rings, the bearing ring material made of high carbon chromium bearing steel is quenched, and then the bearing ring material is tempered at a temperature of 180 to 130 ° C., and further shot peened into the bearing ring material. After processing and surface hardening, there is a method of manufacturing the race ring by further tempering the race ring material at a temperature of 180 to 220 ° C. This method has high toughness, and also has a pressure scar and wear resistance on the surface. A method of the invention for producing a rolling device part having excellent properties (for example, see Patent Document 1) is disclosed.

  Furthermore, the inner and outer rings of the rolling bearing are made of high carbon chrome bearing steel, heat-treated by induction hardening after high temperature tempering after carbonitriding, and a material change resistance layer and a compressive stress of 200 MPa or more are applied to the surface layer. Thus, a method is disclosed in which the rolling fatigue life and crack fatigue strength are greatly improved and can be used stably for a long period of time in applications where repeated bending stress acts (for example, see Patent Document 2).

Furthermore, the rolling element is a high carbon chromium bearing steel, and at least one of the inner ring and the outer ring is martensitic stainless steel. The area ratio of the eutectic carbide contained in the stainless steel is 2 to 7%, and the major axis of the eutectic carbide. Is 30 μm or less, the average value of the equivalent circle diameter of the eutectic carbide is 1.0 to 1.6 μm, the average area of the eutectic carbide is 0.8 to ² μm ² , excellent in quietness, corrosion resistance and lifetime An invention (for example, refer to Patent Document 3) that is a bearing material having the characteristics is disclosed.

  However, these methods are not necessarily a method for mass-producing a small-diameter general-purpose bearing race having a track holding portion around the raceway surface portion that is low in cost and excellent in toughness.

JP 2004-339575 A JP 2004-293632 A JP 2003-222138 A

  Usually, SUJ2 specified in JIS G 4805 of high carbon chromium bearing steel is heated to about 840 ° C. in a quenching furnace so that the hardness becomes HV700 to HV780 in order to obtain a stable rolling fatigue life. It is used after quenching and further tempering. By the way, in this high carbon chromium bearing steel, the core portions of the inner and outer rings of the bearing after hardening are hardened to HV700 or more from the hardenability of the steel type and the mass effect of the thickness of 7 mm or less. For this reason, the inner and outer rings of the completed bearing may be cracked by an impact load. For this reason, it is necessary to take measures such as consideration of the bearing holding structure that receives the impact load and the use of bearing inner and outer rings manufactured by carburizing and quenching heat treatment for applications where the impact load is applied. Therefore, the problem to be solved by the present invention is to improve the toughness of the inner and outer rings for small general-purpose bearings that are hot forged with high carbon chromium bearing steel, and to produce a small-sized general purpose high toughness manufactured by this method. It is to provide inner and outer rings for bearings.

  Means of the present invention for solving the above problems will be described. The means of claim 1 of the present invention is an annular body having a center hole 3 by hot forging by a horizontal high-speed forging device from a cut disc body of a steel bar material 1 of SUJ2 defined in JIS standard G4805 which is a high carbon chromium bearing steel. Then, the annular body 2 is spheroidized and annealed to decarburize the surface layer to a carbon content of 0.20% or less. The annular groove 7 is turned on the annular side surface 5 between the center hole 3 of the annular body 2 that has been decarburized and the outer diameter surface 4 that is the outer periphery of the annular body 2, and the thin wall formed in the annular groove 7 The outer ring element 9 and the inner ring element 10 connected to each other at the portion 8 are formed in a double ring body 11. Next, the thin-walled portion 8 of the double ring body 11 of the outer ring element 9 and the inner ring element 10 is punched out by pressing to be completely separated into the outer ring element 9 and the inner ring element 10.

  Further, raceway surfaces 12 and 13 that are annular raceways are formed on the inner diameter surface of the outer ring shape 9 and the outer diameter surface of the inner ring shape 10 obtained by turning, respectively. In this case, the original SUJ2 material inside the annular body is exposed by turning to separate the carbon content of the annular raceways 12 and 13 into the outer ring element 9 and the inner ring element 10 described above. The carbon contents of these raceway surfaces 12 and 13 appear as 0.95 to 1.10% of the carbon content of the original SUJ2. On the other hand, the carbon content of the outer diameter surface, the inner diameter surface and the surface layer portion of the side surface which is the surrounding track holding portion supporting these raceway surfaces 12 and 13 is left as it is as a decarburized layer of 0.20% or less, and the outer ring The base 9 and the inner ring base 10 are formed. That is, the means of claim 1 has a raceway surface excellent in rolling fatigue life and a high-toughness raceway holding portion, and a forged die for inner and outer races of a small general-purpose bearing having an outer ring outer diameter of φ26 to 41 mm. It is a manufacturing method of material.

  In the present invention, the annular body 2 is spheroidized and annealed by the above-mentioned means, and the outer diameter surface 4, the annular side surface 5, and the inner diameter surface 6 of the annular body 2, which is a forged raw material of high carbon chromium bearing steel, The decarburized layer is formed, and the annular body 2 formed with the decarburized layer is turned so that the inner surface 6 of the outer ring element 9 and the outer surface 4 of the inner ring element 10 are made of SUJ2 material containing about 1% of the original carbon. The outer ring surface 9 has an outer diameter surface 4 and an annular side surface 5, and the inner ring shape 10 has an inner diameter surface 6 and an annular side surface 5 which are hardened by leaving a decarburized layer having a carbon content of 0.20%. The quenching hardness of the decarburized layer part after having been reduced is given to toughness. Therefore, the durability of the track holding portion of these portions is improved and cracking does not occur. On the other hand, the rolling surface portions, that is, the raceway surfaces 12 and 13 have the HV 60 to 63 having sufficient hardness to ensure the rolling fatigue life because the carbon content is maintained around 1% of the original. obtain.

  That is, by the means of the present invention, a low carbon alloy layer is produced seamlessly in the raceway surface holding portion, thereby improving the impact value and lowering the ductility-brittle transition temperature, thereby improving the durability of the finished bearing against impact. It has improved. The portions of the raceway surfaces 12 and 13 that receive repeated loads from the rolling elements have a carbon content of about 1% of that of the original high carbon chrome bearing steel, which is necessary to ensure the rolling fatigue life. Hardness is obtained.

  The means of claim 2 is the non-oxidation annealing furnace in which the carbon content of the surface layer part is reduced to 0.20% or less by spheroidizing annealing in the above means, and the atmosphere is adjusted so as not to cause grain boundary oxidation. In this method, the annular body 2 is repeated and, for example, spheroidized annealing is performed 20 times to obtain a decarburized layer in which the carbon content of the surface layer portion of the annular body 2 is 0.20% or less. In this way, the annular body 2 is repeatedly subjected to spheroidizing annealing in a non-oxidizing annealing furnace adjusted to an atmosphere that does not cause grain boundary oxidation, whereby a sufficient decarburized layer is formed and toughness is obtained. Further, the desired decarburized layer depth can be obtained by adjusting the number of repetitions.

  The means of claim 3 is an inner and outer ring profile for a bearing produced by the method of the means of claims 1 and 2. That is, the carbon content of the raceway surfaces 12 and 13 of the outer ring element 9 and the inner ring element 10 for a small general-purpose bearing made of SUJ2 defined in JIS standard G4805 of high carbon chromium bearing steel is the carbon content of SUJ2. 0.95 to 1.10% of the outer ring element 9 and the carbon content of the surface layer portion of the track holding portion around the raceway surfaces 12 and 13 is decarburized to 0.20% or less and The inner ring element 10 is shown. These are the outer ring shape 9 and the inner ring shape 10 for bearings having the raceway surfaces 12 and 13 having excellent rolling fatigue life and the toughness raceway holding portion. In the present invention described above, the small general-purpose bearing refers to a general-purpose bearing whose outer ring has an outer diameter of φ26 mm to φ41 mm, which is the processing limit on the horizontal high-speed forging device used in the present invention, This size is due to the hardenability of the high carbon chromium bearing steel and the mass effect of the wall thickness of 7 mm or less, and the core portions of the inner and outer rings of the bearing after hardening are hardened to HV700 or more.

  Since the outer ring element and the inner ring element of the small general-purpose bearings manufactured according to the present invention are formed with a decarburized layer of 0.2% or less of the surface layer of the track holding part other than the raceway surface part, the outer ring element of these bearings is formed. When the crushing value of the inner ring element and the inner ring element were measured, the inner ring and outer ring made of the outer ring element and inner ring element of the bearing of the present invention in which the decarburized layer was formed cracked only at a load of 7300 N. The inner and outer rings formed of the outer ring element shape and the inner ring element shape of the conventional bearing not formed on the surface were cracked at a load of 4800N. That is, the outer ring and the inner ring of the bearing according to the present invention have improved toughness against cracking by about 50%. In addition, since these raceway surfaces have the hardness of the raw steel as they are, it is possible to form a small and highly versatile bearing by the method of the present invention, such as having a sufficient rolling fatigue life.

  Embodiments of the present invention will be described with reference to the drawings. In the order of steps (a) to (h) shown in FIG. 1, the mass% of SUJ2 of JIS G4805 standard is C: 0.95 to 1.10%, Si: 0.15 to 0.35%, Mn: A high carbon chromium bearing steel composed of 0.50% or less, P: 0.025% or less, S: 0.025% or less, Cr: 1.30 to 1.60%, the balance Fe and inevitable impurities was processed. That is, while cutting the steel bar material 1 made of the above-mentioned high carbon chrome bearing steel to a required length with a horizontal high-speed forging device, it is hot at a high speed of 100 or more and 170 or less per minute. Forging. The horizontal high-speed forging device used in the present invention has a cutting mechanism for cutting the steel bar 1 into a required length in the device, and transfers a plurality of forging steps to apply pressure to apply the target annular body. 2 was formed into an annular body 2 having a center hole 3, an outer diameter surface 4 and an annular side surface 5 of (b) by hot forging of (a). Next, the annular body 2 is repeatedly spheroidized and annealed, and the carbon content of the surface layer portions of the center hole 3, outer diameter surface 4 and annular side surface 5 of the annular body 2 in (c) is reduced to 0.20% or less. Decarburized. In this case, in the means of claim 2, spheroidizing annealing is to repeatedly spheroidize the annular body 2 in a non-oxidizing annealing furnace adjusted to an atmosphere that does not cause grain boundary oxidation. With a non-oxidizing annealing furnace adjusted to an atmosphere of 0.34% to 1.06%, spheroidizing annealing for 15 hours per time was performed 20 times in total while decarburizing between 800 ° C and 700 ° C for a total of 300 hours. Repeated. In this way, decarburization was performed in a non-oxidation annealing furnace with care not to cause grain boundary oxidation.

  The surface layer portions of the outer diameter surface 4, the annular side surface 5, and the inner diameter surface 6 of the center hole 3 of the annular body 2 of (c) were decarburized to the carbon content of 0.13% by the annealing treatment for 20 times. . Then, the annular side surface 5 of the decarburized annular body 2 is turned parallel to the center hole 3 as shown in (d), and the thin groove portion 8 shown in (e) is formed inside the annular groove 7. A double ring body 11 comprising an outer ring shape 9 and an inner ring shape 10 to be connected is processed. Next, as shown in (f), the thin ring portion 8 of the double ring body 11 of the outer ring element 9 and the inner ring element 10 is punched from the outer ring element 9 to the inner ring element 10 in the direction of the arrow as shown in FIG. The outer ring shape 9 and the inner ring shape 10 were obtained. Further, as shown in (g) and (h), rolling grooves 14 were formed in the outer ring shape 9 and the inner ring shape 10, respectively. In these (e) to (h), the outer diameter surface 4 and the annular side surface 5 of the outer ring shape 9, the inner diameter surface 6 of the inner ring shape 10, and the portions indicated by the dots in the vicinity of the inside of the annular side surface 5 are The decarburized layer formed by repeated spheroidizing annealing is shown.

  The inner diameter of the outer ring shape 9 and the outer diameter of the inner ring shape 10 were turned to finish the outer ring raceway surface 12 and the inner ring raceway surface 13 as shown in FIG. The carbon content of the raceway surface 12 of the outer ring and the raceway surface 13 of the inner ring represents 0.95 to 1.10% of the carbon content of the original SUJ2 steel type. On the other hand, the outer diameter surface 4 and the annular side surface 5 of the outer ring shape 9 and the inner diameter surface 6 of the inner ring shape 10 and the orbital surface holding portion of the annular side surface 5 other than the raceway surfaces 12 and 13 by the spheroidizing annealing 20 times described above. The carbon content of the surface layer was decarburized to 0.13%, and high toughness was obtained in the surface layer of the raceway holding part. The surface layer portions of the track holding portions other than the raceway surfaces 12 and 13 were also turned, and the carbon content of the surface layer portions of these track holding portions was finished to be decarburized to 0.20%. Thus, an inner and outer ring of a small general-purpose bearing having an outer ring outer diameter of φ26 to 41 mm was obtained.

  The inner and outer rings of the small general-purpose bearing obtained above were heated to 840 ° C. in a quenching furnace, quenched into quenching oil, and tempered to make the raceway hardness HV700-780.

  In addition, compared with the method of this invention, in the conventional method by one spheroidizing annealing treatment, the carbon content of the surface layer part of the track holding part other than the track surface was 0.71%.

  According to the method of the present invention in which an annular body of a high carbon chrome bearing steel forged material is subjected to spheroidizing annealing 20 times, and in a conventional method, an annular body of a high carbon chrome bearing steel forged material is subjected to spheroidizing annealing once. 3 and FIG. 4, micrographs of the metal structure in the annealed state of the outer diameter surface portion and the annular side surface portion of the annular body of the high carbon chromium bearing steel forged shape member are compared with those obtained by the above method. It was shown to.

  Furthermore, the micrograph of the metal structure in the quenched state of the annular body of the high carbon chrome bearing steel forged shape material of the present invention that has been subjected to the above 20 repeated annealing treatments is a conventional spheroidizing annealing treatment. FIG. 5 and FIG. 6 show a comparison with a 400 × magnification micrograph of the metal structure of the ring.

  From the respective contrast micrographs of (a) and (b), the outer diameter surface, the inner diameter surface, and the annular side surface of the annular body of the high carbon chrome bearing steel forged shaped body that has been subjected to 20 repeated annealing treatments of the present invention. In each case, a decarburized layer with a reduced amount of carbide was observed compared to the conventional one.

  Furthermore, FIG. 7 (a) shows a comparison of the hardness results on the HV scale in the state where the annular body of the high carbon chromium bearing steel forged base material is annealed and further quenched, in the present invention and the conventional one. , (B) and graphs (a) and (b) of FIG.

  From these graphs, the annular side surface and outer diameter surface of the outer ring element that becomes the raceway surface holding part after turning are annealed and the annular side surface is HV300 or less, and the depth from the annular side surface to the inside is less than HV700. A hard tough layer remains. The outer diameter surface is HV300 or less, and a high toughness layer having a hardness reduced to less than HV700 remains at a depth of 2.0 mm from the outer diameter surface after turning the surface to the inside.

  The depth of the high toughness layer of the raceway surface holding portion of the outer ring shape or inner ring shape of these bearings in the present invention can be adjusted by the annealing time. Furthermore, the high-toughness layer of the outer ring-shaped or inner ring-shaped raceway holding portion of these bearings can also be generated by a method of annealing in iron oxide or steel stone.

It is a figure which shows the manufacturing process of the method of this invention. It is a figure which shows typically the integration state of the outer ring | wheel and inner ring | wheel of the bearing manufactured by this invention. The micrograph of the metal structure in the repeated annealing state of the high carbon chrome bearing steel forged shape material in the present invention is 400 times, and (a) is an outer diameter surface portion and (b) an annular side surface portion. It is a 400-times micrograph of the metal structure in the annealing state of the high carbon chromium bearing steel forging shape in the conventional method, (a) is an outer diameter surface portion, (b) is an annular side surface portion. The micrograph of 400 times in the state which repeatedly annealed the high carbon chromium bearing steel forged shape material in this invention, and also quenched, (a) is an outer diameter surface part, (b) It is an annular side part. The micrograph of 400 times in the state which repeatedly annealed the high carbon chromium bearing steel forge shape material in the conventional method, and also quenched, (a) is an outer diameter surface part, (b) is an annular side surface part. The graph shows the hardness results on the HV scale in a state where the high carbon chrome bearing steel forged shape material in the present invention is annealed and further quenched, (a) is an annular side surface portion and (b) is an outer diameter surface portion. . The graph shows the hardness results on the HV scale in the case where the high carbon chrome bearing steel forged material in the conventional method is annealed and further quenched, with (a) an annular side surface portion and (b) an outer diameter surface portion. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel bar material 2 Annular body 3 Center hole 4 Outer diameter surface 5 Annular side surface 6 Inner diameter surface 7 Annular groove 8 Thin wall part 9 Outer ring element 10 Inner ring element 11 Double ring body 12 Outer ring raceway surface 13 Inner ring raceway surface 14 Roll Groove

Claims (3)

  A high-carbon chromium bearing steel stipulated in JIS standard G4805, a round disc of SUJ2 is formed into an annular body having a center hole by hot forging using a horizontal high-speed forging device, and this annular body is then subjected to spheroidizing annealing. After decarburizing the carbon content of the surface layer to 0.20% or less, the annular side surface of this annular body is turned to form a double annular body of an outer ring shape and an inner ring element shape connected by a thin portion. Next, the thin ring part of the outer ring element and inner ring element double ring is punched out and separated into the outer ring element and inner ring element by turning to the inner ring surface of the outer ring element and the outer ring surface of the inner ring element respectively. The raceway surface is formed, the carbon content of the formed raceway surface is 0.95 to 1.10% of the carbon content of the original SUJ2 of the high carbon chrome bearing steel, and the raceway holding portion around the raceway surface Decarburization with a carbon content of the surface layer of 0.20% or less By leaving the manufacturing method of the inner and outer races formed and fabricated material small general-purpose bearing and forming a track holding portion imparted with high toughness with raceways excellent in rolling fatigue life.   The method of decarburizing the carbon content of the surface layer to 0.20% or less by spheroidizing annealing consists of repeatedly spheroidizing and annealing the annular body in a non-oxidizing annealing furnace adjusted to an atmosphere that does not cause grain boundary oxidation. The method for manufacturing an inner and outer ring shaped member of a small general-purpose bearing according to claim 1.   The carbon content of each raceway surface of the inner and outer ring elements for a small general-purpose bearing made of SUJ2 specified in JIS standard G4805 of high carbon chromium bearing steel is 0.95 to 1.10 of the original SUJ2 carbon content. %, And the carbon content of the surface layer portion of the raceway holding part around the raceway surface is decarburized to 0.20% or less, and it is excellent in rolling fatigue life of small general-purpose bearings Bearing inner and outer ring shaped material having a raceway surface and a tougher raceway holding part.

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