JPH09227930A - Continuous heat treatment apparatus by induction heating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuos heat treatment apparatus by induction heating which can continuously execute tempering heat treatment, etc., needing soaking for long time. SOLUTION: In the continuous heat treatment apparatus by the induction heating, a material W to be heated is heated to a prescribed temp. while shifting from a charging side to a discharging side along the progressing way (X-X) and discharged after holding at a specific temp. for a prescribed time. Further, a temp. raising part coil 10 arranged parallel to both sides of the progressing way (X-X) of the material to be heated and a heat soaking part coil 20 conductively connected to the discharging side end of each of both sides of the temp. raising part coil 10 at its one end part and forming a sectorial shape opened toward the discharging side at the other end part, are provided. The end parts at the charging sides of both sides of the temp. raising part coil 10 are conductively connected and the end parts at the discharging sides of both sides of the heat soaking part coil are also conductively connected to form on induction heating coil 1 of closed circuit with the both sides of the heat raising part coil 10 and the heat soaking part coil 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to induction used for annealing heat treatment of a hardened part by cold working of a nail-shaped part having a head heading processed, and aging heat treatment of precipitation hardening stainless steel. The present invention relates to a continuous heat treatment device by heating.

[0002]

2. Description of the Prior Art When a precipitation hardening stainless steel is cold-worked, such as a shaft pin for an anchor bolt, the toughness of the pin material may cause a neck jump or breakage, resulting in a human injury. In order to prevent this, heat treatment such as tempering or aging only the head and neck of the pin is performed after the head of the pin is processed.To perform such local heat treatment using a normal heat treatment furnace, local masking is performed. Pretreatment such as is required, which increases cost and makes mass production difficult.

Since such local heating is easy with induction heating, for example, a coil for preheating described in Japanese Patent Laid-Open No. 11727/1990 and a heating coil adapted to the shape of the object to be heated are combined. A continuous heat treatment apparatus by induction heating is disclosed. This device transfers semi-continuously in a long preheating coil to raise the temperature, and then intermittently moves to a heating coil that matches the shape of the object to be heated to heat it to the quenching temperature.

[0004]

However, the above-mentioned conventional continuous heat treatment apparatus by induction heating is suitable for short-time heat treatment such as quenching heat treatment of low alloy steel, but solid solution treatment of high alloy steel is required. In heat treatments that require a certain holding time at the heating temperature, such as aging heat treatment or tempering heat treatment, a complicated operation is required for power control, such as adjusting the power applied to the heating coil to keep the temperature constant. There is an inconvenience. Further, since the object to be heated is intermittently sent and heated, there is a problem that the processing capacity is small in the case of large-scale heat treatment of a small object to be heated.

Therefore, an object of the present invention is to provide a heat treatment apparatus by continuous induction heating, which is capable of performing a large number of treatments for objects to be heated, such as tempering treatment, which requires soaking for a long time.

[0006]

In order to achieve the above object, a continuous heat treatment apparatus using induction heating according to the present invention moves an object to be heated along an advancing path from an insertion side to an ejection side and raises it to a predetermined temperature. In a continuous heat treatment apparatus by induction heating that heats and holds at a predetermined temperature for a predetermined time and then discharges, a heating section coil arranged in parallel on both sides of a traveling path of a heated body and a heating section coil having one end on both sides thereof. And a soaking part coil forming a fan shape whose other end is open toward the discharging side, and the other ends of the heating part coils on the insertion side are electrically connected to each other. And the discharge side ends of the heat equalizing section coils on both sides are electrically connected to each other to form a closed-circuit induction heating coil by the heat raising section coils and the heat equalizing section coils on both sides. It is what

That is, the object to be heated inserted through the insertion port is heated while reaching between the parallel heating coils and reaches a predetermined temperature. Subsequently, when the coil moves in the fan-shaped soaking section that opens toward the discharge side, the distance between the induction coil and the heated object gradually increases, so that the temperature rise of the heated object stops and soaking of the heated predetermined temperature is performed. It is discharged from the discharge port while being kept at a constant temperature. That is, heating by appropriately selecting the fan-shaped opening angle and coil length of the soaking section coil,
A heat treatment such as tempering while maintaining a uniform temperature can be continuously processed.

Further, in the continuous heat treatment apparatus by induction heating of the present invention, the object to be heated is heated to a predetermined temperature while moving from the insertion side to the discharge side along the traveling path, and is held at the predetermined temperature for a predetermined time and then discharged. In a continuous heat treatment apparatus using induction heating, a heating portion coil arranged in parallel on both sides of a traveling path of a body to be heated, and one end thereof is electrically connected to each discharge side end of the heating portion coil on the both sides and the other end. And a heat-retaining part having one end electrically connected to the respective discharge-side ends of the heat-uniforming part coils on both sides and arranged in parallel with the traveling path. A coil, the ends on the insertion side of the heat raising unit coils on the both sides are electrically connected to each other, and the ends on the discharge side of the heat retention unit coils on the both sides are electrically connected to each other and Heating part coil, soaking part coil, and heat retaining part coil It is characterized in that to form the induction heating coil of more closed circuit.

That is, as described above, the object to be heated is heated to a predetermined temperature by the heat-raising part coil, stopped at the temperature-uniforming part coil, is held at a predetermined temperature, and is kept parallel to the traveling path. While passing through the heating coil, only the amount of heat radiated by the object to be heated is induction-heated by the heat retaining coil, so that it is more advantageous for holding the heat for a longer time than the case of only the heat equalizing coil.

Further, by setting only the head of the object to be heated of the headed shaft having a head having a diameter larger than that of the shaft so as to move through the induction heating coil, the shaft is not heated easily. It is possible to heat only the head with, and it is possible to perform annealing heat treatment of the hardened part by cold working and aging heat treatment of precipitation hardening type stainless steel without lowering the hardness of the shaft part of the nail-shaped parts etc. Become.

As the object to be heated, a precipitation hardening stainless steel or heat resistant steel having the components as set forth in claim 4 is used at 400 ° C to 75 ° C.
The aging heat treatment of heating to 0 ° C. or the martensitic stainless steel or heat resistant steel of the component according to claim 5 is carried out at 300 ° C.
In the case of tempering or annealing heat treatment of heating to 700 ° C., or in quenching heat treatment of heating the same martensitic stainless steel or heat-resistant steel to 960 ° C. to 1200 ° C., the heating temperature is [diameter (mm) × 3se
It is suitable for the case of heat treatment for holding for more than c]. In the case of such a high alloy steel, quenching and solid solution and aging require more time than the low alloy steel, so it is necessary to maintain the heating temperature for some time. (M
This is because a predetermined heat treatment effect can be obtained by holding for at least m) × 3 sec].

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings. FIG. 1 is a perspective view showing the overall configuration of a continuous heat treatment apparatus by induction heating according to the first embodiment of the present invention, and FIG. 2 is a plan view of a heating coil of the continuous heat treatment apparatus by induction heating according to the first embodiment of the present invention as seen from above. , FIG. 3 is FIG.
FIG. 4 is a view as viewed from an arrow A in FIG.

In these drawings, the induction heating coil 1 of the continuous heat treatment apparatus is composed of a heating part coil 10 on the insertion side and a heating part coil 20 on the discharge side. The heating part coil 10 includes two conductor coil members 11 and 12 arranged in parallel at equal intervals on both sides of the traveling path X-X line of the object W to be heated.
The insertion side end portions 11a and 12a are connected by the insertion side connecting portion 13 so as to be electrically connected to each other.
The coil member 11 on one side of the heating part coil 10 is cut near the central part with a gap between the insertion side 111 and the discharge side 112, and the terminal 14 is cut at the cutting end 11b of the insertion side 111.
However, the terminal 15 is conductively fixed to the cut end 11c of the discharge side 112. The terminals 14 and 15 are connected to a high frequency power source (not shown).

The soaking section coil 20 is composed of two conductor coil members 21 and 22 as in the heating section coil 10,
One end 21a of the coil member 21 is on the discharge side end 11d of the coil member 112 of the heating part coil 10, and one end 22a of the coil member 22 is the other end 1 of the coil member 12 of the heating part coil 10.
2b are electrically connected to each other. The other ends 21b and 22b of the coil members 21 and 22 form a fan shape that opens toward the discharge side. In the present embodiment, the traveling paths are formed in a fan shape that is open at equal intervals, but may be asymmetric depending on the shape of the object to be heated or when it is desired to provide a temperature difference between both sides of the object to be heated. And the other end 21 of the outlet
b and 22b are connected by a discharge side connecting portion 23 so as to be electrically connected. With the above configuration, the current flowing in the induction heating coil 1 passes from the terminal 14 to the terminal through the coil member 111, the insertion side connecting portion 13, the coil member 12, the coil member 22, the discharge side connecting portion 23, the coil member 21 and the coil member 112. It is electrically connected to 15 to form a circuit of an induction heating coil. The object to be heated W which is inserted into the induction heating coil 1 having such a configuration from its insertion opening (left side in FIG. 1) is
By a transfer device (not shown), the central portions of the heat raising coil 10 and the heat equalizing coil 20 are continuously moved from the insertion port to the discharge port (right side in FIG. 1) along the line X-X.

The operation of the continuous heat treatment apparatus having the above structure will be described below. With the high-frequency current applied to the induction heating coil 1, the object W to be heated is moved from the insertion port into the heating section coil 10 along the traveling path XX by a transfer device (not shown). Then, the object W to be heated is heated by the induced current, and the temperature thereof rises as it goes to the discharge side, and reaches a substantially predetermined temperature at the connection point between the heating part coil 10 and the soaking coil 20. Further, the object W to be heated moves into the soaking part coil 20, but if the soaking part coil 20 is parallel, the temperature of the object W to be heated rises steadily due to the magnetic flux of the induction coil and exceeds a predetermined temperature. Therefore, it is difficult to maintain the uniform temperature at a predetermined temperature. However, in the configuration of the present invention, the soaking section coil 20 opens in a fan shape toward the discharge side,
As the heated body W advances toward the discharge side, the distance between the coil members 21 and 22 of the soaking part coil 20 and the heated body W increases, the effect of induction heating decreases, and the temperature of the heated body W rises. Is reduced. Therefore, if the length of the heat equalizing part coil 20 and the fan-shaped opening angle are appropriately selected and only the temperature decrease due to the heat radiation of the object W to be heated is compensated by the heating of the heat equalizing part coil 20, the temperature of the object W to be heated is increased. Will move while being held constant. This makes it easy to maintain a constant temperature for a long time such as tempering.

[0016]

Example A heating experiment was conducted on the continuous induction heating apparatus having the above-described structure under the following conditions. Object to be heated: Material Precipitation hardening type stainless steel: Headed pin of size 7.5φ × 3.5 + 5φ × 70 (Fig. 5) Induction heating coil: Coil length of heating section 100mm: Coil length of soaking section 105mm Feed rate: 5 mm / sec Frequency: 18 kHz Target heating temperature: 680 ° C. Experimental method: A thermocouple was brought into contact with the head of a headed pin of a moving heated object to measure the temperature change.

Curve A in FIG. 6 represents the relationship between the position of the heating coil and the measured temperature as an experimental result. As shown by the curve A in the figure, when the temperature exceeds the bending point of the connecting portion between the heating portion coil 10 and the soaking portion coil 20, the temperature rise decreases and the temperature stabilizes at about 680 ° C. to the discharge side. A curve B in the drawing shows the result of the simulation of the assumed temperature when the soaking part coil 20 does not open in a fan shape and has a parallel shape. That is, when the heating coil has only the parallel portion over the entire length, the temperature continues to rise to the discharge side as shown by the curve B in the figure.
It is difficult to maintain a constant temperature as in the continuous induction heating device of the present invention.

As described above, according to the continuous heat treatment apparatus of the embodiment of the present invention, the heating portion coil parallel to the traveling path of the object to be heated and the heating portion coil fan-shaped toward the discharge side are provided. Since the object to be heated which has been heated to the predetermined temperature by the heating part coil is reduced to the discharge side, the effect of the induction heating of the heating part coil is reduced, and it can be heated by the amount of the temperature decrease due to heat dissipation. . As a result, the object to be heated can be moved to the discharge side while being kept at a constant temperature. Therefore, by appropriately selecting the length and the opening angle of the soaking section coil, it is possible to continuously perform the heating and the constant temperature induction heating with one coil.

Further, if only the head of a headed shaft member such as a nail-shaped component such as an anchor bolt shaft pin is set so as to move through the induction heating coil, the shaft portion can be heated easily. Only the head can be heated without doing so, and the aging heat treatment of the head can be performed without reducing the hardness of the shaft, and accidents such as jumping of the neck during execution can be prevented. Although many precipitation hardening stainless steels are used for the shaft pin for the anchor bolt, according to the continuous heat treatment apparatus of the present invention, by selecting the coil length and the feeding speed appropriately, [diameter of heated object (mm)
× 3 sec] or more, and the solution hardening and aging heat treatment of the precipitation hardening stainless steel can be continuously performed.

FIG. 7 is a conceptual plan view of the induction heating coil of the second embodiment. In the above first embodiment, FIG.
As shown in FIG. 5, the heating target W is discharged from the end of the uniform heating part coil 20 opened in a fan shape, but in the second embodiment, the parallel part is further extended from the discharge side end of the uniform heating part coil 20. The heat retaining coil 30 having the above is provided, and the object to be heated is discharged from the discharge port after passing through the heat retaining coil 30. In the present embodiment, the heat retaining coil 30 is parallel, but it may be fan-shaped with an angle different from that of the heat equalizing coil 20. The heating coil of the present embodiment is effective when the object to be heated is kept warm for a longer time.

[0021]

As described above, since the continuous heat treatment apparatus of the present invention is provided with the heating portion coil parallel to the traveling path and the heating portion coil which opens in a fan shape toward the outlet side, The temperature of the heating element rises when moving in the parallel heating coil, and as the fan-shaped heating coil moves to the discharge side, the heating effect of the heating coil decreases and the temperature rise stops, and the temperature rises to a constant temperature. It moves while being held and is discharged from the discharge port. That is, by appropriately selecting the length and opening angle of the fan-shaped heat equalizing section coil, the object to be heated is heated only by continuously moving it through one heating coil without changing the additional power of the induction heating coil. It is possible to maintain a constant temperature, which is particularly effective in the case of mass heat treatment such as tempering of small parts. In particular, when it is used for heat treatment and heating of the head of a precipitation hardening stainless headed pin, it is possible to prevent accidents such as neck breakage due to insufficient toughness. Further, by adding the heat retaining coil after the heat equalizing coil, it becomes possible to maintain the temperature for a longer time.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of a continuous induction heating apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view of a heating coil of the continuous induction heating device according to the first embodiment of the present invention as seen from above.

FIG. 3 is a view taken in the direction of arrow A in FIG. 2;

FIG. 4 is a view taken in the direction of arrow B in FIG. 2;

FIG. 5 is a view showing the shape of a heated headed pin used in an example of the present invention.

FIG. 6 is a diagram showing a result of a heating experiment of an example of the present invention.

FIG. 7 is a plan view showing the concept of a heating coil of a continuous induction heating device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Induction heating coil 10 Heating part coil 11 Coil member 12 Coil member 13 Insertion side connection part 14 Terminal 15 Terminal 20 Uniform heat part coil 21 Coil member 22 Coil member 23 Discharge side connection part 30 Heat retention part coil 31 Coil member 32 Coil Member 33 Discharge side connection part 111 Heat rising part insertion side 112 Heat rising part discharge side W Heated object (headed pin)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H05B 6/44 H05B 6/44

Claims (5)

[Claims] 1. A continuous heat treatment apparatus using induction heating, which heats an object to be heated to a predetermined temperature while moving from the insertion side to the discharge side along an advancing path, discharges after holding the temperature at the predetermined temperature for a predetermined time, The heating section coils arranged in parallel on both sides of the advancing path, and one end is electrically connected to the discharge side ends of the heating section coils on both sides, and the other end forms a fan shape open toward the discharging side. And a soaking section coil for connecting the insertion side ends of the heating section coils on both sides to each other in conduction, and connecting the discharge side ends of the heating section coil on both sides to each other for conduction. A continuous heat treatment apparatus by induction heating, characterized in that a closed-circuit induction heating coil is formed by the heating section coil and the soaking section coil on both sides. 2. A continuous heat treatment apparatus by induction heating in which an object to be heated is heated to a predetermined temperature while moving from the insertion side to the discharge side along an advancing path, is held at the predetermined temperature for a predetermined time, and is then discharged. The heating section coils arranged in parallel on both sides of the advancing path, and one end is electrically connected to the discharge side ends of the heating section coils on both sides, and the other end forms a fan shape open toward the discharging side. And a heat retaining coil arranged in parallel to the traveling path, one end of which is electrically connected to the respective discharge side ends of the heat equalizing coils on both sides,
The both ends of the heating section coils on the insertion side are electrically connected to each other, and the ends of the heating section coils on the discharge side are electrically connected to each other to form the heating section coils on both sides. A continuous heat treatment apparatus by induction heating, characterized in that an induction heating coil of a closed circuit is formed by a soaking section coil and a heat retaining section coil. 3. The object to be heated is a headed shaft member having a head portion having a diameter larger than that of the shaft portion, and only the head portion is set so as to advance in the induction heating coil. Item 1
Alternatively, the continuous heat treatment apparatus by induction heating described in 2. 4. The object to be heated, C: 0.1 wt% or less, Si: 1.0 wt% or less, Mn: 2.0 wt% or less, Ni: 3.0-27.0 wt% Cr: 12.0-18. In addition to 0 wt%, Cu: 0.25 wt% or less V: 0.5 wt% or less Nb: 0.45 wt% or less Ti: 2.5 wt% or less Al: 1.5 wt% or less B: 0.01 wt% or less Alternatively, after heating precipitation hardening type stainless steel or heat resistant steel containing all elements and remaining Fe and unavoidable impurities to 400 ° C. to 750 ° C., at the same temperature, [diameter of heated object (mm) × 3 sec] or more time The continuous heat treatment apparatus by induction heating according to any one of claims 1 to 3, which is intended to perform an aging heat treatment for holding. 5. The object to be heated C: 0.3 to 1.2 wt% Si: 0.35 to 3.5 wt% Mn: 0.35 to 1.25 wt% Ni: 2.5 wt% or less Cr: 7 0.0 to 21.0 wt%, Mo: 1.3 wt% or less Cu: 0.30 wt% or less Pb: 0.3 wt% or less Se: 0.3 wt% or less, including any or all elements, and remaining Fe In addition, in the tempering or annealing heat treatment of heating martensitic stainless steel or heat-resistant steel consisting of unavoidable impurities to 300 ° C to 700 ° C, or the quenching heat treatment of heating it to 960 ° C to 1200 ° C, the heating temperature becomes (Mm) × 3 sec] The continuous heat treatment apparatus by induction heating according to any one of claims 1 to 3, which is intended to perform a heat treatment for holding for a time of at least 3 mm.