JPH0331415A - High-frequency hardening device - Google Patents

Abstract

PURPOSE:To stably produce the high-frequency hardened product which is free from unequal hardening and quenching crack by providing a heating coil and cooling liquid spraying nozzle in a device for rotating a material to be treated and using a device provided with a heating control means and primary and secondary cooling means at the time of subjecting a cast iron cam shaft, etc., to a high-frequency hardening. CONSTITUTION:The cam shaft made of cast iron, cast steel, etc., is fixed and supported to a cam shaft rotating and supporting mechanism and the circumference of the cam shaft is partially covered with a coil for high-frequency induction heating; in addition, the cam shaft is subjected to the high-frequency induction beating to an austenitization temp. region by the heating control means at the time of subjecting the above- mentioned cam shaft to the high-frequency induction heating. A cooling liquid for hardening is then sprayed form a nozzle to the material to be treated to gently cool the material down to the Ms point at which the structure transforms to martensite or below. The cam shaft is then cooled again by spraying the cooling liquid from the nozzle in the amt. smaller than before after the spraying of the cooling liquid is once interrupted. The cam shaft or the like is thus hardened at a high yield by the hardening device which allows the hardening by the high-frequency induction heating with which the unequal hardening and quenching crack are prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an induction hardening device for induction hardening a heat-treated material such as an engine camshaft made of materials such as cast iron and cast steel. .

(Prior art) Generally, metal parts that require strength, such as the camshaft of a vehicle engine, have been subjected to heat treatment such as induction hardening to increase the strength of the parts. . In this heat treatment such as induction hardening, the material to be heat treated, such as a camshaft, is heated with high frequency to a high temperature of, for example, 900°C to change the metal structure of the material to austenite, and then rapidly cooled at a cooling rate higher than the critical cooling rate. According to
It is a heat treatment that generates a martensitic structure and makes it extremely hard and strong.1. It is known that good heat treatment effects can be obtained when steel materials such as carbon steel are induction hardened.

However, when engine camshafts, etc. are made of cast iron, and this cast iron heat-treated material is induction hardened in the same way as steel materials such as carbon steel, quench cracking occurs due to the expansion of the martensitic structure during martensitic transformation. Because of this tendency, it is difficult to stabilize the hardening quality of cast iron heat-treated materials that have been subjected to induction hardening treatment.

Therefore, when mass-producing induction hardened products made by applying induction hardening to cast iron heat-treated materials, yields tend to be low, making it difficult to increase the mass production of cast iron induction hardened products. .

(Problem to be solved by the invention) When heat-treated materials such as engine camshafts are made of cast iron, and this cast iron heat-treated material is induction hardened in the same way as steel materials such as carbon steel, quenching cracks occur. It is difficult to stabilize the hardening quality of cast iron heat treated materials that have been induction hardened, so when mass producing induction hardened products that have undergone induction hardening treatment of cast iron heat treated materials, However, there was a problem in that the yield rate was poor and it was difficult to increase the mass production of induction hardened cast iron products.

This invention was made in view of the above-mentioned circumstances, and it is possible to uniformly perform induction hardening treatment over the entire circumference of the heat-treated material, thereby preventing the occurrence of uneven hardening, and making it possible to prevent the occurrence of uneven hardening. The purpose of the present invention is to provide an induction hardening device that can stabilize the hardening quality of heat-treated materials that are prone to quench cracking when induction hardened, and increase the mass productivity of induction hardened products made of cast iron. be.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a support mechanism that rotatably supports a material to be heat treated, a rotational drive mechanism that rotationally drives the material to be heat treated supported by this support mechanism, and A heating coil for high-frequency heating that locally covers the periphery of the material to be heat treated; a nozzle for spraying cooling liquid onto the material to be heat treated; a heating control means for high-frequency heating to a high temperature state to austenite; and a heating control means for spraying a cooling liquid from a nozzle at a predetermined flow rate to the high-frequency heated material to be heat-treated to make the material to be martensitic; A primary cooling control means performs primary cooling relatively slowly to below the Ms point at which it transforms into a structure, and after this primary cooling, appropriate cooling liquid spraying is stopped for a period of time. and a second cooling control means for cooling the heat-treated material by spraying it again onto the heat-treated material at a flow rate smaller than the flow rate during the first cooling.

(Function) During induction hardening, the rotary drive mechanism is driven and the heating coil is used to high-frequency heat the material to be heat-treated to a high temperature state that turns it into austenite.Then, the cooling liquid is sprayed from the nozzle onto the material to be heat-treated that has been high-frequency heated. The heat-treated material is first cooled relatively slowly by spraying at a predetermined flow rate to below the Ms point at which the heat-treated material transforms into a martensitic structure, and after this first cooling, appropriate cooling liquid spraying is stopped. Spraying cools the heat-treated material by spraying the cooling liquid from the nozzle again at a flow rate smaller than the flow rate during the primary cooling, thereby cooling the heat-treated material made of cast iron. In addition to stabilizing the quenching quality of heat-treated materials that are prone to quench cracking when induction hardened, and increasing the mass production of cast iron induction-hardened products, the rotary drive mechanism rotates and drives the heat-treated materials. By performing the induction hardening process, the material to be heat treated is uniformly subjected to the induction hardening process over the entire circumference, thereby preventing the occurrence of uneven heating.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 schematically show the overall structure of an induction hardening apparatus according to an embodiment of the present invention.

That is, as shown in FIG. 2, the induction hardening apparatus of this embodiment is provided with a first processing section 1, a second processing section 2, a third processing section 3, and an annealing section 4, respectively. These first processing section 1, second processing section 2, third processing section 3, and slow cooling section 4 are each provided independently, and as shown in FIG. The material to be heat treated is transported between the first processing section 1 and the second processing section 2 by the first transport mechanism 6 and the second processing section 2.
a second transport mechanism 7 between the processing section 2 and the third processing section 3;
, a third transport mechanism 8 between the third processing section 3 and the slow cooling section 4
It is designed to be transported sequentially by in this case,
The camshaft 5, which is a material to be heat treated, is made of a material such as cast iron or cast steel. The cam shaft 5 has cam portions 5b protruding and recessed at a plurality of locations on the substantially cylindrical shaft body 5a.

Further, the first processing section 1 includes a first support mechanism 9 that rotatably supports a heat-treated material such as a camshaft 5, and a heat-treated material such as a camshaft 5 supported by the first support mechanism 9. A first rotational drive mechanism 10 that rotationally drives a material, a plurality of first heating coils 11 for high-frequency heating that locally covers the periphery of a material to be heat treated such as a camshaft 5, and a camshaft 5 and the like. A plurality of first spray nozzles 12 for spraying the cooling liquid onto the heat-treated material are respectively provided. In this case, the first heating coils 11... have a substantially semicircular cross section as shown in FIG.
... are arranged at positions corresponding to the cam portions 5b... of the camshaft 5, respectively. Further, for the first spraying, nozzles 12 are appropriately arranged around the camshaft 5, for example, on the top, bottom, left and right sides. Further, the first rotation drive mechanism 10 and the first heating coils 11 are connected to a heating control means 14 of a control section 13 formed by, for example, a microcomputer and its peripheral circuits. The heating control means 14 controls the operations of the first rotational drive mechanism 10 and the first heating coil 11 . Furthermore, this control section 13 includes a heating control means 1.
4, a primary cooling control means 15, a secondary cooling control means 16, and a heating means 17, which will be described later, are provided, respectively.

Further, for the first spraying, the tip of the liquid feeding passage 19 of the first cooling liquid control mechanism 18 is connected to the nozzle 12 . The first coolant control mechanism 18 is provided with a liquid feeding pump (not shown) connected to the base end side of the liquid feeding passage 19, a flow rate control valve (not shown) interposed in the liquid feeding passage 19, and the like. Ori,
In the first spraying, a predetermined flow rate of the cooling liquid is supplied to the nozzle 12 via the first cooling liquid control mechanism 18 . In this case, the coolant is cooled at a temperature below a predetermined state change temperature (for example, about 74 degrees Celsius or 90 degrees Celsius), which is lower than the Ms point (for example, about 200 degrees Celsius) at which the heat-treated material such as the camshaft 5 transforms into a martensitic structure. A hardening agent (for example, polyalkylene glycol (PAG)) that is uniformly mixed in a liquid (for example, water) and separated from the base liquid at a high temperature above the state change temperature is used at a predetermined concentration. .In addition to this, oil,
It may also be made of vinyl or the like.

Furthermore, this first coolant control mechanism 18 is connected to the first cooling control means 15 of the control section 13 . The primary cooling control means 15 is further connected to a first transport mechanism 6, a first temperature sensor 20a, and a second temperature sensor 20b, respectively.

In this case, the first temperature sensor 20a is in a high temperature state (9
The second temperature sensor 20b is in the state of being subjected to high frequency heating (high frequency heating temperature) to a temperature of about 00°C (approx. (first cooling temperature).

Further, the second processing section 2 includes a first support mechanism 9 of the first processing section 1, a first rotational drive mechanism 10. A second support mechanism and a second rotary drive mechanism 21 having substantially the same configuration as the nozzles 12 are provided for the first spraying, and a nozzle is provided for the second spraying. In this case, the second spraying nozzle of the second processing section 2 is connected to a second cooling liquid control mechanism 22 having substantially the same configuration as the first cooling liquid control mechanism 18 of the first processing section 1. There is.

The second rotational drive mechanism 21 and the second coolant control mechanism 22 of the second processing section 2 are connected to the secondary cooling control means 16 of the control section 13.

A second transport mechanism 7 and a third temperature sensor 20c are further connected to the secondary cooling control means 16, respectively. In this case, the third temperature sensor 20c detects a state in which the quenching agent in the coolant is lowered to a predetermined state change temperature (for example, about 74°C or 90°C) at which it is uniformly mixed into the base liquid (secondary cooling). temperature).

Furthermore, the third processing section 3 includes a support mechanism 9 for the first processing section 1, a first rotational drive mechanism 10, a first heating coil 11, and a first rotational drive mechanism 10.
A third support mechanism, a third rotational drive mechanism 23, a second heating coil 24, and so on, each having substantially the same configuration as . . . , are provided. In this case, the third rotational drive mechanism 23, second heating coil 24, . . . of the third processing section 3 are connected to the tempering heating means 17 of the control section 13. A third conveyance mechanism 8 is further connected to this temper heating means 17.

Next, the operation of the induction hardening apparatus having the above configuration will be explained.

First, during induction hardening of a material to be heat treated, such as the camshaft 5 of an engine, the material to be heat treated, such as the camshaft 5, is first set on the first support mechanism 9 of the first processing section 1. Then, when the power switch (not shown) of the induction hardening device is turned on in this state, the heating control means 14 of the control section 13 controls the first
The first rotational drive mechanism 10 of the processing unit 1 is driven, the camshaft 5 is rotationally driven, and the first heating coil 11 is
... is energized, and the camshaft 5 is high-frequency heated by the first heating coils 11. Further, the operation signal of this heating control means 14 is outputted to the primary cooling control means 15.

Further, the heating control means 1 is added to the primary cooling control means 15.
When the operation signal from 4 is input, the first temperature sensor 2
Based on the detection signal from 0 m, the metal structure of the heat-treated material such as the camshaft 5 becomes austenite (900 m
At the point in time (indicated by A in FIG. 5) when a state of high-frequency heating is detected (indicated by A in FIG. 5) (approximately 1 heating coil 11... is cut off, and
Subsequently, a drive signal is output to the first coolant control mechanism 18, and a predetermined flow rate of coolant is supplied to the nozzles 12 through the first coolant control mechanism 18, and the first spraying is performed. 1
In the spraying, the cooling liquid is sprayed from the nozzles 12 to the heat-treated material such as the camshaft 5, and the heat-treated material such as the camshaft 5 is cooled. In this case, the coolant sprayed onto the heat-treated material such as the camshaft 5 is heated to a temperature higher than the predetermined state change temperature (for example, about 74°C or 90°C) at which the quenching agent is uniformly mixed into the base liquid. Since it is heated, in this state, the quenching agent in the coolant separates from the base liquid, and this quenching agent forms a coating layer (film) on the surface of the material to be heat treated, such as the camshaft 5. Therefore, the coating layer (film) of the quenching agent component can prevent the base liquid of the coolant from evaporating from the surface of the heat-treated material such as the camshaft 5, so the cooling rate can be adjusted (delayed). can.

Further, when the second temperature sensor 20b detects a state in which the material to be heat treated, such as the camshaft 5, is subjected to primary cooling above and below the Ms point where it transforms into a martensitic structure (indicated by B in FIG. 5), The drive of the first coolant control mechanism 18 is stopped by the control signal from the primary cooling control means 15, and a drive stop signal to the first rotary drive mechanism 10 is output to the heating control means 14, After the drive of the first rotational drive mechanism 10 is stopped, a drive signal is subsequently output to the first transport mechanism 6. Then, the material to be heat treated, such as the camshaft 5, is transported from the first processing section 1 to the second processing section 2 by this first transport mechanism 6, and is transferred to the second support mechanism of this second processing section 2. Set. Note that during the time during which the first transport mechanism 6 transports the heat-treated material such as the camshaft 5 (B-- in FIG.
Between C), the spraying of the coolant is stopped, and the materials to be heat treated, such as the camshaft 5, are gradually cooled in an air-cooled state.

Further, when the material to be heat treated such as the camshaft 5 is set on the second support mechanism of the second processing section 2, the secondary cooling control means 16
The second rotational drive mechanism 21 of the second processing section 2 is driven, and the camshaft 5 is rotationally driven.A drive signal is output to the second coolant control mechanism 221, and this second coolant In the second spraying, a predetermined flow rate of cooling liquid is supplied to the nozzle via the control mechanism 22, and in the second spraying, the cooling liquid is sprayed from the nozzle to the heat-treated material such as the camshaft 5. The material to be heat treated is cooled. In this case, in the second spraying, the flow rate of the coolant sprayed from the nozzle is set to a smaller flow rate than the flow rate during the first cooling, and cooling is performed more slowly than during the first cooling (cooling time is relatively long). Then, at the time when it is detected by the third temperature sensor 20c that the material to be heat treated such as the camshaft 5 has been cooled to the secondary cooling temperature (indicated by D in FIG. 5),
The drive of the second coolant control mechanism 22 is stopped, and a drive stop signal is output to the second rotation drive mechanism 21, so that the drive of the second rotation drive mechanism 21 is stopped. In this case, when the third temperature sensor 20c detects that the material to be heat treated, such as the camshaft 5, has been cooled to the secondary cooling temperature, the material to be heat treated, such as the camshaft 5, is in a predetermined state of the coolant. Since the temperature is lowered below the change temperature (for example, about 74° C. or 90° C.), all of the quenching agent in the coolant is evenly mixed into the base liquid. Therefore, when the material to be heat treated such as the camshaft 5 is cooled to the secondary cooling temperature, the quenching agent component formed on the surface of the material to be heat treated such as the camshaft 5 between A and C in FIG. All of the coating layer (film) of the quenching agent component can be peeled off from the surface of the material to be heat treated such as the camshaft 5, so the coating layer (film) of the quenching agent component can be removed from the surface of the material to be heat treated such as the camshaft 5.
It is possible to prevent the film from being retained in the formed state.

Further, after the driving of the second coolant control mechanism 22 and the second rotational drive mechanism 21 is stopped, a drive signal is subsequently output to the second transport mechanism 7. The second transport mechanism 7 transports the heat-treated material such as the camshaft 5 from the second processing section 2 to the third processing section 3.
is set on the third support mechanism. When the material to be heat treated, such as the camshaft 5, is set on the third support mechanism of the third processing section 3, the third rotation drive mechanism 23 of the third processing section 3 is activated by the tempering heating means 17. The camshaft 5 is driven to rotate, and the second heating coil 24.
... is energized, and the material to be heat-treated, such as the camshaft 5, is high-frequency heated by the second heating coil 24 to an appropriate tempering temperature, and tempering is performed.

Furthermore, after the tempering process is finished, the tempering heating means 17 turns the second heating coil 24 of the third processing section 3 on.
... is cut off and the driving of the third rotational drive mechanism 23 is stopped, and then the third transport mechanism 8 is driven. The second transport mechanism 7 transports the heat-treated material, such as the camshaft 5, from the third processing section 3 to the annealing section 4, where it is annealed.

Therefore, in the case of the above structure, during induction hardening, the material to be heat treated, such as the camshaft 5, is heated by the first heating coil 11 while the first rotation drive mechanism 10 is driven by the heating control means 14. The material to be heat-treated, such as the camshaft 5, is subjected to high-frequency heating to a high-temperature state where it becomes austenitic, and then the primary cooling control means 15 sprays the cooling liquid at a predetermined flow rate from the nozzles 12. The material to be heat treated, such as the camshaft 5, is first cooled relatively slowly to below the Ms point at which the material to be heat treated transforms into a martensitic structure, and after this first cooling, the camshaft By transporting the heat-treated material such as No. Since the material to be heat treated such as the camshaft 5 is cooled by spraying it again at a flow rate smaller than the flow rate during cooling, the cooling rate of the material to be heat treated such as the camshaft 5 during induction hardening work can be reduced. It can be adjusted relatively gently (in the direction of delay). Therefore,
It is possible to stabilize the quenching quality of heat-treated materials such as cast iron camshafts 5 that are susceptible to quenching cracks when induction hardened, and to increase the mass productivity of cast iron induction-hardened products. can.

Furthermore, during induction hardening work, the first Second. Since the third rotary drive mechanism 10, 21, 23 rotates the material to be heat treated, such as the camshaft 5, the material to be heat treated, such as the camshaft 5, can be uniformly induction hardened over its entire circumference. It is possible to prevent uneven baking. Also, the first
processing section 1, second processing section 2, third processing section 3, slow cooling section 4. are provided independently, and the heat-treated materials such as the camshaft 5 are separated from each other. Since the conveyance mechanism 6 of s1, the second conveyance mechanism 7, and the third conveyance mechanism 8 are configured to sequentially convey between each processing section, it is possible to carry out a series of induction hardening operations in a single treatment tank. In comparison, it is possible to improve work efficiency and increase mass productivity. Furthermore, the first heating coil 11 of the first processing section 1 is connected to the cam section 5b of the camshaft 5.
Since they were placed locally at positions corresponding to...
The hardness of the cam portions 5b can be further increased compared to the shaft body 5a of the camshaft 5, and the durability of the camshaft 5 can be improved.

Note that this invention is not limited to the above embodiments. For example, in the above embodiment, the first processing section 1, the second processing section 2, the third processing section 3, and the slow cooling section 4 are each provided independently, and the material to be heat treated, such as the camshaft 5, is transferred to the first transport section. Although a configuration in which the mechanism 6, the second conveyance mechanism 7, and the third conveyance mechanism 8 are used to sequentially convey the material between each processing section is shown, in the case of small-scale production, a series of induction hardening processes can be performed in a single treatment tank. It may be configured to perform the work. Furthermore, it goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] According to the present invention, there is a support mechanism that rotatably supports a material to be heat treated, a rotary drive mechanism that rotationally drives the material to be heat treated supported by the support mechanism, and a rotation drive mechanism that locally supports the material to be heat treated. A heating coil for high-frequency heating that covers the area, a nozzle for spraying cooling liquid onto the heat-treated material, and a high-temperature state where the heating coil turns the heat-treated material into austenite while driving the rotation drive mechanism. a heating control means for high-frequency heating, and a cooling liquid is sprayed from a nozzle at a predetermined flow rate to the high-frequency heated material to be heat-treated, so that the material to be heat-treated is transformed into a martensitic structure;
The m primary cooling control means performs primary cooling relatively slowly to below point s, and after this primary cooling, appropriate cooling liquid spraying is stopped for a period of time, and the said spraying is performed to perform the primary cooling of the cooling liquid from the nozzle. The heat-treated material 1 is sprayed at a smaller flow rate than the flow rate when the heat-treated material is heated, and a secondary cooling control means for cooling the heat-treated material by blowing again is provided, so that the heat-treated material is induction hardened uniformly over the entire circumference. can be applied to prevent uneven baking.
It is possible to stabilize the quenching quality of heat-treated materials that tend to cause quench cracking when induction hardened, such as cast iron heat-treated materials, and to increase the mass productivity of cast iron induction-hardened products.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a specific configuration diagram of the control section, FIG. 2 is a schematic configuration diagram of the entire induction hardening device, and FIG. 3 is a cam in the first processing section. FIG. 4 is a front view showing the state of attachment of the shaft, FIG. 4 is a side view of the same, and FIG. 5 is a characteristic diagram showing the temperature change state of the heat-treated material during induction hardening. 5... Camshaft (heat treated material), 9... First support mechanism, 10... First rotational drive mechanism, 11... First heating coil, 13... Control unit, 14... Heating control means, 15... Primary cooling control means, 16... Secondary cooling control means.

Claims (1)

[Claims] A support mechanism that rotatably supports a material to be heat treated, a rotation drive mechanism that rotationally drives the material to be heat treated supported by the support mechanism, and a heating coil for high frequency heating that locally covers the periphery of the material to be heat treated. , a spray nozzle for spraying a cooling liquid onto the material to be heat treated, a heating control means for high frequency heating the material to be heat treated to a high temperature state that austenitizes the material to be austenitized by the heating coil while the rotation drive mechanism is driven; and high frequency heating. A cooling liquid is sprayed at a predetermined flow rate from the spray nozzle onto the heat-treated material to relatively slowly primary cool the heat-treated material to below the Ms point at which the heat-treated material transforms into a martensitic structure. a primary cooling control means; after the primary cooling, the cooling liquid is applied to the heat-treated material from the spray nozzle at a flow rate smaller than the flow rate during the primary cooling through an appropriate cooling liquid spraying stop time; and secondary cooling control means for cooling the material to be heat treated by spraying the material again.