JPH06248346A - Austempering treatment for industrial fastener - Google Patents

Abstract

PURPOSE:To secure the rise in the temp. of a fastener product in the method for austempering treatment for an industrial fastener by high frequency induction heating. CONSTITUTION:A chute 20 is constituted of a magnetic body, and its temp. is raised by induction heating. On this chute 20, the stock of an industrial fastener is advanced and is fed into a high frequency induction current generating coil 30, and the stop of the advance of the stock by the operation of an induction current, induction heating, the start of the advance of the stock after its attainment to a magnetic transformation point and additional temp. rising heating are executed. Immediately after its passing through the high frequency induction current generating coil 30, the stock is cast to a compact salt tank 40 and is rapidly cooled, and austempering treatment of an industrical fastener is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an austempering treatment method for industrial fasteners (industrial fastening products) using high frequency induction heating.

[0002]

BACKGROUND OF THE INVENTION Industrial fasteners are SAE1050-1.
It is made of a material equivalent to 095, and is austempered (heat treatment using an austenite region) in order to obtain necessary properties such as springiness and hardness. The present applicant previously proposed the following austempering treatment method for industrial fasteners in Japanese Patent Application No. 3-175863 (June 21, 1991). That is, the industrial fastener material is advanced on the insulating chute and sent into the high frequency induction current generating coil, the progress of the material is stopped by the action of the induction current, the induction heating, the progression of the material after reaching the magnetic transformation point. A method for austempering industrial fasteners, in which starting, additional heating by heating is performed, and immediately after passing through the high frequency induction current generating coil, the material is put into a small salt tank and rapidly cooled.

[0003]

However, the conventionally proposed austempering method for fastener products has the following problems. That is, when the fastener product is induction-heated on the insulating chute, if the thickness of the fastener product is thin, the heat radiation amount per unit volume becomes large, and the magnetic transformation point (for example, 76
It is difficult to raise the temperature when approaching 0 ° C. Therefore, it becomes difficult to perform stable austempering.

An object of the present invention is to provide an austempering method for industrial fasteners, which can easily raise the temperature of the fastener product to a temperature above the magnetic transformation point, regardless of the shape and thickness of the fastener product. .

[0005]

The above object can be achieved by the following method for austempering industrial fasteners of the present invention. That is, the material of the industrial fastener is advanced on the chute and sent into the high frequency induction current generating coil, the progress of the material is stopped by the action of the induction current, induction heating, and the progress of the material after the magnetic transformation point is reached. In an austempering method for industrial fasteners, in which the raw material is put into a small salt bath immediately after passing through the high frequency induction current generating coil and rapidly cooled, the chute is made of a magnetic material and the high frequency is applied. An austempering method for industrial fasteners, characterized in that the chute is extended into the induction current generating coil and induction-heated by the high frequency induction current generating coil before the material of the industrial fastener is advanced on the chute.

[0006]

In the method of the present invention, the industrial fastener is advanced on the vibrating chute and fed into the high-frequency induction current generating coil, where the progress of the induction current is automatically stopped, internal heat generation is started, and the temperature is increased. When reaches the magnetic transformation point of the material, the process automatically starts again. Thus, the material reaches an austemperable temperature, eg 830 ° C,
After passing through the high-frequency induction current generating coil, it dropped from the chute end and put into a salt bath containing the salt solution kept at 300 ° C to 400 ° C, rapidly cooled, and austempered.

According to the present invention, since the chute is made of a magnetic material and the chute is also induction-heated, when the fastener passing therethrough is induction-heated, the amount of heat absorbed by the chute is larger than the amount of heat released, so that the temperature drop of the fastener is reduced. The fastener easily heats up to the austemperable temperature.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of an austempering method for industrial fasteners according to the present invention will be described below with reference to the drawings. As shown in FIG. 1 and FIG. 2, the austempering apparatus of the embodiment of the present invention comprises a feeder 10 for sequentially supplying materials for industrial fasteners, a chute 20 for conveying the supplied industrial fastener materials, and fastener feeding of the chute 20. High-frequency induction current generation coil 3 provided near the rear end in the direction
0, and a salt tank 40 provided below the rear end of the chute 20.

The feeder 10 has a bottom wall 12 and a substantially cylindrical side wall 14, and is composed of a ball having a step portion 16 formed in a spiral shape on the side wall, and a minute high frequency vibration is applied to the ball. . The bottom wall 1 is the fastener material to be austempered.
When the ball is put in the second stage and vibration is imparted to the ball, the fastener material is sequentially fed up on the chute 20 by going up the step portions 16 of the side wall 14 one by one in a row.

The chute 20 is made of a magnetic material and a conductive material in order to enable induction heating. Shoot 20
Has a groove for feeding the fastener material in one row, and a minute high frequency vibration is applied thereto. The fastener material sent from the feeder 10 is conveyed on the chute 20 by vibration. The chute 20 extends into the high frequency induction current generating coil 30, and is heated by induction by the coil 30 to generate about 80
The temperature is raised in advance to a temperature of 0 ° C. or higher.

The high frequency induction current generating coil 30 is connected to a high frequency current generating device 32. The high frequency induction current generating coil 30 is arranged so as to wind the chute 20 at intervals, generates a high frequency induction magnetic field inside, and applies a high frequency induction current to the fastener material (conductive material) conveyed on the chute 20. At the same time, the conveyance is automatically braked and heating is started. However, when the fastener material reaches the magnetic transformation point (about 783 ° C) of the fastener material in a very short time (within 2-3 seconds), the brake is automatically released and the fastener material is conveyed again. The product heating temperature can be controlled by suppressing the passage time of the induction current coil after the progress of the work.
Then, the fastener material is controlled to be heated to 830 ° C. In this case, since the temperature of the chute 20 is high and the amount of heat absorbed by the chute is larger than the amount of heat released, the temperature of the fastener material is suppressed from falling and the temperature is easily heated to 830 ° C.

Since it takes only a few seconds to heat the fastener material from room temperature to 830 ° C., the oxidation of the fastener material from the start of heating to the start of cooling by the salt solution causes almost no problem. However, when complete non-oxidation is required, the area from the high frequency induction current generating coil 30 to the salt bath fall is sprinkled with N ₂ gas or the like, or at least the area is covered with a box and the inside of the box is covered. It may be filled with N ₂ gas.

The salt bath 40 is at least one, four in the figure, small-sized baths having a heat insulating layer wall, and comprises a salt solution inside. The salt layer 40 has a length of several tens of centimeters and is smaller than a conventional one having several meters. The salt solution is controlled to an austemper temperature (300-400 ° C) by an appropriate heating means. Salt tank 4
0 contains a basket 42, and at least one of the baskets 42 is located below the chute end so that it can receive the fastener material heated and falling from the chute end. There is. The basket 42 that is not below the chute end is the salt tank 4
The fastener 4 that has been removed from 0 and has undergone the austempering process is removed from the basket 42 and is now empty basket 4
2 can be inserted into the salt bath 40 again.

Due to the downsizing of the salt bath 40 and the reduction of the heat capacity of the furnace, the rise of the temperature rise of the furnace is accelerated. In addition, it is necessary to change the salt solution temperature in order to change the cooling rate of the fastener material depending on the thickness of the fastener material, which can be done in about 10 minutes, which took several hours in the conventional furnace heating method. And work efficiency goes up.

Next, a method for austempering an industrial fastener using the above apparatus will be described. Feeder 10
From this, by vibrating the balls, the fastener materials are continuously supplied onto the chute 20 one by one. The fastener material supplied onto the chute 20 is conveyed by vibrating the chute 20 and fed into the area inside the high frequency induction current generating coil 30. Coil 30 of chute 20
The portion extending inward is induction-heated by the coil 30 and heated to about 800 ° C. or higher. The fastener material fed into the coil 30 is automatically stopped by the action of the induced current and is induction heated, and moves again after the heating temperature reaches the magnetic transformation point of the fastener material. Utilizing this phenomenon, the fastener material is heated to 830 ° C.
Immediately after overheating, the overheated fastener material is put into the small salt tank 40 from the end of the chute 20 to 300 ° C-400.
Quench to austemper temperature in the ° C range. When the austempering process is completed, the basket 42 is placed in the salt bath 4
The fastener product is taken out from the basket 42. The emptied basket 42 is returned to the salt tank 40 and is again arranged below the end of the chute 20. The above is continuously performed.

[0016]

According to the above method of the present invention, the following effects are obtained. I. Since the chute is induction heated as a magnetic chute, the temperature drop of the fastener material can be reduced, and the fastener material can be easily heated to a temperature above the magnetic transformation point regardless of the shape or thickness of the fastener material. Can be made. B. By applying the high frequency induction heating to the heating, the heating equipment can be extremely miniaturized from the furnace of several meters in the case of the conventional furnace heating to the coil of several cm of the present invention. C. This makes it possible to use 80% or more of the input energy for heating the fastener material without the need to heat the furnace body, and to use the energy more effectively than the conventional use of about 20-30% of the input energy. Be peeled off.

D. About 3.5m thick due to high frequency heating
Fastener materials up to m can be rapidly and evenly heated in a few seconds, and in the case of the conventional furnace heating, the work efficiency and the heat treatment quality can be improved as compared with the case of heating in a unit of several minutes. E. Rapid heating, followed by rapid cooling in the salt bath,
Oxidation of fastener material no longer has to be a real problem and atmospheric heating can now be performed.

[Brief description of drawings]

FIG. 1 is a schematic side view of an apparatus for performing an austempering method for industrial fasteners according to an embodiment of the present invention.

2 is a cross-sectional view of a chute portion of the austempering device for the industrial fastener of FIG.

[Explanation of symbols]

 10 feeder 20 chute 30 high frequency induction current generating coil 40 salt tank

Claims (1)

[Claims] 1. A material for industrial fasteners is advanced on a chute and sent into a high frequency induction current generating coil, and the progress of the material is stopped by the action of induction current, induction heating,
Starting the progress of the material after reaching the magnetic transformation point, allowing additional heating to be performed, and immediately after passing through the high frequency induction current generating coil, the material is put into a small salt tank and rapidly cooled, an austempering method for industrial fasteners In, the chute is made of a magnetic material and extends into the high frequency induction current generating coil, and the chute is induction heated by the high frequency induction current generating coil before the material of the industrial fastener is advanced on the chute. An austempering method for industrial fasteners, characterized in that