Apparatus and method for quenching steel balls

Abstract

The present invention provides a steel ball quenching apparatus and method that can quench steel balls easily, quickly, in large quantities, and reduce decarburization of the steel ball surface and CO2 emissions. [Solution] A steel ball hardening apparatus 10 is provided, comprising a rotary table 13 on a base 14 with a plurality of cylinders 12 surrounding it for housing steel balls 11, a high-frequency heating coil 15 for heating the steel balls 11, a hole 14h provided in the base 14 at the end of the high-frequency heating coil 15 corresponding to the bottom of the cylinder 12 in the rotational direction of the rotary table, and a hardening water tank 16 provided below the base 14.

Description

Technical Field

[0001] The present invention relates to a quenching device and a quenching method for steel balls used in hub bearings of automobiles and the like.

Background Art

[0002] Conventionally, quenching of steel balls used in hub bearings of automobiles and the like has been performed by furnace quenching. A large number of steel balls were put into a heating furnace, heated at 830°C to 850°C, and the furnace was rotated to perform quenching evenly while heating. However, when performing furnace quenching, there were problems such as a long heating time and a large amount of CO2 generation. There was also a problem that decarburization occurred on the surface of the steel balls, and it was necessary to shave the surface by about 0.1 mm.

[0003] Therefore, in order to reduce the CO2 emission amount during heating, improve work efficiency, reduce product costs, and improve quality, a method and an apparatus for quenching steel balls by high frequency have been developed (see Patent Document 1).

[0004] Patent Document 1 describes, in "Method and Apparatus for Air-Floating High-Frequency Quenching of Steel Balls", "Preheat the steel ball (5) in a metal cylindrical body (7) corresponding to the substantially central portion (21) of the high-frequency heating coil (8), and then, at the upper end face position (23) of the cylindrical body, the steel ball is air-floated and rotated by the electromagnetic force generated between the steel ball and the heating coil, and uniformly high-frequency heated, and then the steel ball is rapidly cooled by a cooling means (3) to form a uniform quenching hardened layer on the surface of the steel ball." (Abstract) (see FIG. 2 attached to the present application).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The aerial levitation high-frequency induction hardening apparatus for steel balls described in Patent Document 1, as shown in Figure 4, has a mechanism in which "the lifting and transferring device 19 connected to the steel ball mounting table 18 inserts the steel ball 5 into the cylindrical body 7, stops it at the preheating position 21 which is the central position of the heating coil 8, preheats it at this position 21, then raises it to the levitation heating start position 22, and simultaneously with the start of levitation heating, moves downward and stops at a predetermined position outside the cylindrical body 7," and "the horizontal transferring device 20 connected to the lifting and transferring device 19 descends from inside the cylindrical body 7 simultaneously with the start of levitation heating, moves the steel ball mounting table 18 which has stopped outside the cylindrical body 7 horizontally together with the lifting and transferring device 19, and stops it at a position in which the naturally falling steel ball 5 and the steel ball mounting table 18 do not interfere with each other" (see paragraphs

[0029] and

[0030] ). As such, it requires complex operation and has the problem that it is difficult to harden a large number of steel balls quickly.

[0007] Therefore, the object of the present invention is to provide a steel ball quenching apparatus and quenching method that can quench steel balls easily, quickly in large quantities, and reduce decarburization of the steel ball surface and CO2 emissions. [Means for solving the problem]

[0008] To solve the above problems, the present invention employs the following means. (1) A steel ball quenching apparatus comprising a rotating table on a base, the rotating table having a plurality of cylinders for housing the steel balls arranged around it, a high-frequency heating coil for heating the steel balls, a hole provided in the base at the end of the high-frequency heating coil in the rotational direction of the rotating table corresponding to the bottom of the cylinders, and a quenching water tank provided below the base. (2) The steel ball quenching apparatus according to (1), wherein the high-frequency heating coil for heating the steel ball is provided above and below the rotating table, sandwiching a plurality of cylinders for housing the steel ball. (3) A method for quenching steel balls, comprising using a rotary table having a plurality of cylinders for housing the steel balls arranged around it, and while rotating the rotary table on a base, heating the steel balls with a high-frequency heating coil, and then dropping them into a quenching water tank provided below the base through holes in the base corresponding to the bottom of the cylinders to quench them. [Effects of the Invention]

[0009] The steel ball quenching apparatus and quenching method of the present invention enable the simple, rapid quenching of large quantities of steel balls, resulting in reduced decarburization of the steel ball surface and reduced CO2 emissions. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing a quenching apparatus according to one embodiment of the present invention. [Figure 2] Figure 2 is a conceptual diagram of Figure 1 when it is cut along line AA. [Figure 3] Figure 3 is a conceptual diagram of Figure 1 when it is cut along the line BB. [Figure 4] Figure 4 shows an embodiment of the aerial levitation high-frequency induction hardening apparatus described in Patent Document 1. [Modes for carrying out the invention]

[0011] A quenching apparatus according to one embodiment of the present invention (hereinafter referred to as "this embodiment") will be described with reference to Figure 1.

[0012] The steel ball quenching apparatus 10 according to this embodiment includes a rotary table 13 on a base 14 with a plurality of cylinders 12 surrounding it for housing steel balls 11, a high-frequency heating coil 15 for heating the steel balls 11, a hole 14h provided in the base 14 at the end of the high-frequency heating coil 15 corresponding to the bottom of the cylinder 12 in the rotation direction C of the rotary table 13, and a quenching water tank 16 provided below the base 14.

[0013] The steel ball quenching method according to this embodiment includes a rotary table 13 with a plurality of cylinders 12 surrounding it for housing the steel balls 11. While the rotary table 13 is rotated on a base 14, the steel balls 11 are heated with a high-frequency heating coil 15, and then dropped through holes 14h in the base 14 corresponding to the bottom of the cylinders 12 into a quenching water tank 16 located beneath the base 14 to quench them.

[0014] More specifically, the quenching apparatus 10 includes a base 14 fixed by fixing means (not shown), a rotary table 13 on the base 14 and provided parallel to the base 14, with a plurality of cylinders 12 for housing the iron balls 11 arranged around the rotation direction C, a rotary drive unit 18 that positions the rotary table 13 on the base 14 and is capable of rotating the rotary table 13 in the circumferential direction C about the central axis CL, a high-frequency heating coil 15 provided above and below the rotary table 13 and heating the iron balls 11 which are provided on either side of the plurality of cylinders 12 for housing the iron balls 11, a hole 14h provided at the end of the high-frequency heating coil 15 in the base 14 corresponding to the bottom of the cylinders 12 in the rotation direction C of the rotary table 13, and a quenching water tank 16 provided below the hole 14b and below the base 14.

[0015] Multiple cylinders 12 provided on the rotary table 13 house the steel balls 11. The steel balls 11 housed in the cylinders 12 come into contact with (are placed on) the base 14, and as the rotary table 13 rotates, they rotate simultaneously within the cylinders 12 when it moves in the rotational direction C. One end of the high-frequency heating coil 15 (the lower end of the iron ball 11) is embedded in the base 14, and the other end (the upper end of the iron ball 11) is fixed above the rotary table 13 by fixing means (not shown).

[0016] It is preferable that the high-frequency heating coil 15 for heating the steel balls 11 be installed above and below the rotary table 13, sandwiching a plurality of cylinders 12 that house the steel balls 11. The number of cylinders 12 that house the steel balls 11 is preferably as large as possible in order to quickly harden a large quantity of steel balls 11, and can be 10 to 30 in the direction of rotation C. The high-frequency heating coil 15 is preferably provided above and below the rotary table 13, sandwiching about half of those many cylinders 12. However, it is not limited to the position as shown in FIG. 2, and any position where the steel balls can be sufficiently heated is acceptable.

[0017] The material of the cylinder 12 is preferably a ceramic such as alumina, and the materials of the rotary table 13 and the base 14 are preferably resins. There should preferably be a gap between the steel ball 11 and the cylinder 12. The steel ball 11 rotated by the rotary table 13 rotates by the Lorentz force during heating by the high-frequency heating coil 15 and is heated uniformly.

[0018] The size of the steel ball 11 heated by the high-frequency heating coil 15 can be from 8 to 50 mm. The frequency of the high-frequency heating coil 15 is preferably 3 to 25 kHz, the heating temperature of the steel ball 11 by the high-frequency heating coil 15 is preferably 900 to 1100 °C, and the heating time is preferably 10 to 20 seconds. The rotation speed of the rotary table 13 is preferably 1 rpm or more. However, the rotation speed can be appropriately set according to the diameter of the table (= the number of steel balls that can be set at one time), the length of the coil, the size of the balls, etc.

[0019] When the steel ball 11 is heated by the high-frequency heating coil 15 while the rotary table 13 is rotated on the base 14 and then dropped into the quenching water tank 16 provided under the base 14 from the hole 14h of the base 14 corresponding to the bottom of the cylinder 12 for quenching, one hole 14h in the base 14 is sufficient. As described above, the high-frequency heating coil 15 can be provided above and below the rotary table 13, sandwiching about half of those many cylinders 12 (for example, in the case of FIG. 1, 9 out of 18 cylinders 12). However, the hole 14h in the base 14 is preferably provided at the right end, which is near the end where heating by the high-frequency heating coil 15 is completed, as shown in FIG. 1.

Example

[0020] Steel balls with a diameter of about 8.73 mm, which are SUJ2 spheroidized annealing materials, were heated at a frequency of 25 kHz by a high-frequency heating coil and quenched. The rotary table rotated at 3 rpm directly beneath the coil, and the heating time for each steel ball was set to 10 seconds. The maximum temperature after 10 seconds was approximately 960°C. In actual measurements, the heat treatment of 12 steel balls was completed in 10 seconds (approximately 0.8 seconds per steel ball). Steel balls were heat-treated and then dropped into a quenching water bath for hardening. Various measurements were then performed on the hardened steel balls.

[0021] (result) The core was completely hardened (martensite + undissolved carbides). Compared to conventional products (furnace-heated products), the amount of carbonized material was lower. The surface hardness was 62-67 HRC. No decarburization was observed on the surface of the steel balls. [Industrial applicability]

[0022] The quenching apparatus and quenching method of the present invention are effective for quenching steel balls, and the quenched steel balls can be used in automobile hub bearings and the like, thus having high industrial applicability. [Explanation of Symbols]

[0023] 10. Hardening apparatus for steel balls 11 steel ball 12 cylinders 13 Rotating Table 14 Foundation 14h hole 15. High-frequency heating coil 16. Quenching water tank

Claims

1. A steel ball quenching apparatus comprising a rotating table on a base, the rotating table having a plurality of cylinders arranged around it for housing the steel balls, a high-frequency heating coil for heating the steel balls, a hole provided in the base at the end of the high-frequency heating coil in the rotational direction of the rotating table corresponding to the bottom of the cylinders, and a quenching water tank provided below the base.

2. The steel ball quenching apparatus according to claim 1, wherein the high-frequency heating coil for heating the steel ball is provided above and below the rotating table, sandwiching a plurality of cylinders for housing the steel ball.

3. A method for quenching steel balls, comprising using a rotary table having a plurality of cylinders arranged around it for housing the steel balls, and while rotating the rotary table on a base, heating the steel balls with a high-frequency heating coil, and then dropping them into a quenching water tank provided below the base through holes in the base corresponding to the bottoms of the cylinders to quench them.

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