JP2009155685A - Quenching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quenching method which can reduce the distortion that occurs while being quenched, by inhibiting ununiform cooling (cooling unevenness) from occurring in each which has been immersed in a cooling liquid. <P>SOLUTION: This quenching method includes: three-dimensionally arranging a plurality of workpieces 7 which are heated to a quenching temperature, in a mesh-like tray 8b of a mesh-like basket 8, in such a transversely-placed state that both end faces direct upward and downward; immersing the above basket 8 into a cooling liquid 2 which flows from the bottom part of a cooling tank 3 towards the upper part, by lowering the above basket 8; and quenching the workpieces to harden them. At this time, the workpieces 7 are immersed in the cooling liquid 2 which flows from the bottom part of the cooling tank 3 towards the bottom part 8a of the basket 8, in such a state that a distributor 9 which leads the cooling liquid 2 to a side face side of the basket 8 covers at least the bottom part 8a of the basket 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a quenching method for mechanical parts such as bearings.

Machine parts such as bearings are subjected to quenching treatment in order to obtain necessary mechanical strength and fatigue strength. And when mass-producing these machine parts, in order to improve the productivity, for example, as shown in FIG. 3, it is filled with a cooling liquid 102 such as mineral oil, and the wing 110 is rotated by the stirring pump 104. A large number of heated works (processed objects) 107 three-dimensionally stored in the basket 108 as shown in FIG. 4 are immersed in the cooling tank 103 in which the liquid flow is directed upward from the tank bottom 103a. Therefore, a method of quenching a large amount of work 107 at a time is adopted.
In such a mass quenching method, the work 107 must be arranged in a dense manner in the basket 108, and the liquid flow at the individual placement positions is different. Therefore, non-uniform cooling (cooling unevenness) occurs in each work 107. There arises a problem that the heat treatment strain increases. As a result, defective products with excessive distortion occurred, leading to a decrease in productivity.

  In order to solve this problem, for example, it is proposed that after the workpiece is cooled in a cooling tank for a short time, it is subjected to restraint quenching in which the workpiece is cooled by being pushed into a sizing die by a pusher (see Patent Document 1). .

JP-A-9-176740

  However, even if constrained quenching as in Patent Document 1 is performed, it is difficult to completely suppress the occurrence of distortion, and for those with excessive distortion, further steps such as sizing and quench press are performed to correct the distortion. There was a need to do. In addition, the restraint quenching requires a separate pushing device having a sizing die and a pusher, which increases the manufacturing cost.

  The present invention has been made in view of such circumstances, and reduces distortion generated during quenching by suppressing the occurrence of non-uniform cooling (cooling unevenness) in individual workpieces when immersed in a coolant. It aims to provide a quenching method that can be done.

  In the quenching method of the present invention, a plurality of workpieces that are heated to a quenching temperature are three-dimensionally arranged in a mesh-like basket in a horizontal posture with both end surfaces directed vertically, and the basket is lowered. A quenching method in which the workpiece is hardened by immersing the workpiece in a coolant flowing upward from the bottom of the cooling bath and rapidly cooling, and the cooling flows from the bottom of the cooling bath toward the bottom of the basket The workpiece is immersed in the cooling liquid in a state where at least a bottom surface portion of the basket is covered with a baffle plate that guides the liquid to a side surface side of the basket.

  According to the quenching method of the present invention, when the mesh basket containing a large amount of workpieces is lowered and immersed in the cooling liquid, the bottom surface of the basket is covered with the current plate to cover the basket from the bottom of the cooling tank. The coolant flowing toward the bottom surface can be guided to the side surface of the basket. As a result, it is possible to prevent turbulent flow from occurring near the bottom surface due to high-speed coolant entering the basket through the bottom surface of the basket. The occurrence of unevenness can be suppressed. As a result, it is possible to reduce distortion that occurs when the workpiece is quenched.

In the quenching method, it is preferable that the work is immersed in the cooling liquid in a state where the lower portion of the side surface of the basket is further covered with the current plate, and the height of the side surface of the basket is less than or equal to 1/2 of the current plate. More preferably, the workpiece is immersed in the cooling liquid in a state where it is covered.
In this case, the coolant enters the inside from the middle of the basket in the horizontal direction and circulates in the basket three-dimensionally, so that the coolant can be prevented from staying inside the basket. This can further suppress the occurrence of non-uniform cooling (cooling unevenness) in each workpiece.

  According to the quenching method of the present invention, when the workpiece is immersed in the cooling liquid, at least the bottom surface of the basket is covered with the baffle plate and the flow of the cooling liquid is guided to the side surface of the basket, so It is possible to suppress the occurrence of (cooling unevenness), thereby reducing the distortion generated during quenching of the workpiece. As a result, the processing time of the post-process (for example, polishing process) is shortened, and it is not necessary to perform the sizing and quench press processes, leading to a reduction in manufacturing cost.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a longitudinal side view schematically showing a quenching apparatus used in a quenching method according to one embodiment of the present invention. A quenching apparatus 1 in FIG. 1 includes a cooling tank 3 in which oil is stored as a cooling liquid 2, an agitation pump 4 that is disposed adjacent to the cooling tank 3 and circulates by stirring the cooling liquid 2, and this agitation A duct 5 that guides the coolant 2 stirred by the pump 4 to a discharge port 3a provided at the bottom of the cooling tank 3, and a rectifying guide 6 that adjusts the flow of the coolant 2 from the discharge port 3a toward the top. And.

A method of quenching a steel annular work (object to be processed) 7 using the quenching apparatus 1 is as follows.
The workpiece 7 is accommodated in the basket 8, and a current plate 9 is installed on the lower surface of the bottom surface portion 8 a of the basket 8. The basket 8 containing the workpiece 7 is placed in a heating furnace (not shown) while being placed on the current plate 9, and the workpiece 7 is heated to a high temperature above the transformation point. FIG. 2 is a longitudinal side view for explaining the basket 8 and the current plate 9 of FIG.

  The basket 8 is of a type that can accommodate a large amount of workpieces 7 three-dimensionally. The workpiece 7 is, for example, a rolling bearing race that is an annular member. A plurality of workpieces 7 are placed on a mesh-like tray 8b so that both end faces thereof are directed vertically and do not contact each other, and the tray 8b on which a plurality of workpieces 7 are placed in this manner is a basket. 8 are stacked in multiple stages in the vertical direction at a predetermined interval. Thereby, the workpiece 7 is three-dimensionally arranged in the mesh basket 8. Here, the lowermost tray 8 b constitutes the bottom surface portion 8 a of the basket 8.

  The rectifying plate 9 guides the coolant 2 flowing from the discharge port 3 a at the bottom of the cooling tank 3 toward the bottom surface 8 a of the basket 8 to the side of the basket 8. The rectifying plate 9 is formed into a bowl shape with a metal plate such as iron so as to cover the bottom surface portion 8a of the basket 8 and the lower portion of the side surface of the basket 8, and each of the bottom plate 9a and four sides of the bottom plate 9a And a side plate 9b extending in the vertical direction. The side plates 9b are connected to each other, and the lower portion of the basket 8 is accommodated in a space surrounded by the side plates 9b and the bottom plate 9a. It is preferable that the height h of the side plate 9b is set to 1/2 or less of the height H of the basket 8, and the current plate 9 covers the half or less of the height H of the basket 8 in FIG. The height h of 9b is set to about 1/3 of the height H of the side surface of the basket 8.

  On the other hand, in the quenching apparatus 1, the stirring pump 4 is started, the blades 10 are rotated, and the flow of the coolant 2 upwards from the discharge port 3 a at the bottom of the cooling tank 3 by the rectifying guide 6 (arrow in FIG. 1). Make a). Then, the basket 8 provided with the rectifying plate 9 is lowered and immersed in the coolant 2 of the cooling tank 3. Thus, the workpiece 7 is rapidly cooled and hardened by being exposed to the flow of the coolant 2.

  At this time, the bottom surface 8a of the basket 8 in which a large amount of workpieces 7 are accommodated is lowered while being covered with the rectifying plate 9 and immersed in the cooling liquid 2. The coolant 2 flowing toward the bottom surface portion 8a can be guided to the side surface side of the basket 8. Thereby, it is possible to prevent the occurrence of turbulent flow in the vicinity of the bottom surface portion 8a due to the coolant 2 having a high flow velocity entering the basket 8 through the mesh of the bottom surface portion 8a of the basket 8. Generation of non-uniform cooling (cooling unevenness) in the work 7 can be suppressed. As a result, it is possible to reduce distortion generated when the workpiece 7 is quenched.

  Further, since the rectifying plate 9 further covers the lower portion of the side surface of the basket 8, the coolant 2 hitting the bottom plate 9 a of the rectifying plate 9 is guided to the side surface side of the basket 8 and then along the side plate 9 b. It flows toward the top (arrow b in FIG. 1), enters sideways from the middle stage not covered by the side plate 9b (arrow c in FIG. 1), and cools the inside of the basket 8 three-dimensionally. As a result, the stagnation of the liquid flow that tends to occur in the vicinity of the middle stage of the basket 8 can be prevented, so that the occurrence of uneven cooling (cooling unevenness) in each workpiece 7 can be further suppressed.

  When the rapid cooling is completed, a tempering process of heating at a relatively low temperature is performed. After that, a polishing process is performed as a subsequent process, but since the distortion generated during quenching is reduced, the polishing time can be shortened, and further, such as sizing and quench press applied to excessive deformation There is no need to perform additional steps.

  Thus, in the quenching method of the present invention, the bottom surface portion 8a of the mesh-like basket 8 in which a large amount of work 7 is three-dimensionally accommodated is lowered and immersed in the coolant 2 while being covered with the current plate 9. Therefore, the coolant 2 flowing from the bottom of the cooling bath 3 toward the bottom 8 a of the basket 8 can be guided to the side of the basket 8 by the rectifying plate 9. Thereby, it is possible to prevent the cooling liquid 2 having a high flow velocity from entering the basket 8 and to generate a turbulent flow, and thus it is possible to suppress non-uniform cooling (cooling unevenness) in each workpiece 7. As a result, since distortion generated when the workpiece 7 is quenched can be reduced, it is possible to reduce a polishing allowance in a polishing process as a subsequent process. This shortens the processing time and eliminates the need for the sizing and quench pressing steps that are performed when the strain is excessive, leading to a reduction in manufacturing costs.

The quenching apparatus 1 is not limited to the above-described embodiment, and can be appropriately changed within the scope of the present invention. In the above embodiment, oil is used as the cooling liquid 2, but the cooling liquid 2 can use water, molten salt, or the like in addition to oil. Moreover, although the stirring pump 4 is provided only on one side of the cooling tank 3, it may be provided on both sides.
Further, depending on the heat treatment conditions, only the bottom surface portion 8a of the basket 8 may be covered with the rectifying plate 9.

It is a vertical side view which shows typically the hardening apparatus in this invention. It is a vertical side view explaining the basket of FIG. 1, and a baffle plate. It is a longitudinal cross-sectional view which shows the conventional hardening apparatus typically. It is a perspective view explaining the accommodation state of the workpiece | work in the basket in the conventional hardening method.

Explanation of symbols

1 Quenching device 2 Coolant (oil)
3 Cooling tank 4 Stirring pump 5 Duct 6 Rectification guide 7 Workpiece (object to be treated)
8 Basket 8a Bottom part 9 Current plate

Claims (3)

A plurality of workpieces heated to the quenching temperature are three-dimensionally arranged in a mesh-like basket in a horizontally placed posture with both end faces directed vertically, and the basket is lowered from the bottom of the cooling tank. A quenching method in which the workpiece is hardened by being immersed and rapidly cooled in a coolant flowing upward,
The workpiece is immersed in the coolant in a state where at least the bottom surface of the basket is covered with a baffle plate that guides the coolant flowing from the bottom of the cooling tank toward the bottom of the basket to the side of the basket. A quenching method characterized by that.   The quenching method according to claim 1, wherein the workpiece is immersed in the cooling liquid in a state in which the lower portion of the side surface of the basket is further covered with the current plate.   The quenching method according to claim 2, wherein the work is immersed in the cooling liquid in a state in which the current plate covers half or less of the height of the side surface of the basket.

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