JPH0115565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves continuously feeding a deformed material having portions with different cross-sectional areas in the longitudinal direction onto a conveying line including a quenching zone and a tempering zone. The present invention relates to a tempering method for tempering a deformed material whose predetermined surfaces have been surface hardened by low-frequency induction heating in a tempering zone.

When surface hardening is applied to a specified surface of a member,
Tempering must be applied to the surface-hardened part, but if the part is a mass-produced product, the part must be continuously fed onto a conveyor line that includes a hardening zone and a tempering zone, and then hardened and tempered on the conveyor line. A method of continuously applying is adopted. In this case, a tunnel-shaped electric furnace is installed in the heat treatment line, and if you want to achieve the same effect as the tempering treatment that takes more than 30 minutes by placing it in a normal electric furnace, it is necessary to install a tunnel-shaped electric furnace on the heat treatment line. Since the process becomes long and takes a long time, it is recommended to use low-frequency induction heating, which can heat and temper the part to a predetermined tempering temperature while the part is transported over an extremely short distance. ing.

This type of heat treatment line will be explained with reference to FIG. 1a.

In the figure, reference numeral 1 denotes a conveying device, which consists of, for example, sprockets 11 and 11 that are arranged at a predetermined distance and rotate in the same direction, and an endless chain belt 12 stretched between the two sprockets 11 and 11. ing. The chain belt 12 has at least a quenching zone QZ at the front in the running direction and a tempering zone TZ at the rear.
It is extended as if passing through. For example, a material to be treated where a surface hardening layer is to be formed on the A′ side.
W' is continuously supplied and placed on the upper surface of the outbound traveling start end side of the chain belt 12 with the A' side facing upward, and the front workpiece W' and the rear workpiece
W' is transported on the chain belt 12 with its rear end and front end touching each other, and during transport, first in the quenching zone QZ, the A' side is fixed by a heating coil C ₁ of the end-face heating type connected to the high frequency power source EH. After being induction heated to the quenching temperature, a quenching layer is formed on the A' side by spraying the quenching liquid onto the A' side from the cooling device 3 connected to the quenching liquid supply source P,
Next, it reaches the tempering zone TZ, is carried into a multi-turn induction heating coil _C2 connected to a low frequency power source EL, and is heated to a predetermined tempering temperature while passing through the induction heating coil _C2 , Alternatively, after the temperature is raised, the temperature is maintained for a short period of time to perform a tempering treatment, and the material is discharged from the heat treatment line at the end of the forward path of the chain belt 12. Reference numeral 4 denotes an outer shell made of a heat insulating material for insulating the inside of the coil and covering the outer periphery of the induction heating coil C ₂ for tempering.

By the way, when the above-mentioned heat treatment apparatus hardens and tempers the A' side of the workpiece W' having the shape shown in FIG. 1b, it is possible to form a uniform hardened layer on the A' side. For example, when side A of a deformed material having portions with different cross-sectional areas in the longitudinal direction as shown in Fig. 1c is quenched and tempered,
In the treated A-side, the Aa side part became a quench-hardened layer that was harder than the Ab-side part, and it was extremely difficult to form a uniform quench-hardened layer over the entire A-side.

The present inventor solves the above-mentioned drawbacks that exist when heat treating a profiled material W in the heat treatment line, and provides a continuous induction tempering method for a profiled material that can form a homogeneous hardened layer on the surface to be hardened. be.

In making the present invention, the present inventor has determined that the hardness of the surface A of the deformed material before tempering, which has been quenched in the quenching zone QZ of the heat treatment line, is that formed by high-frequency surface heating and rapid cooling, and that heating coil
Since C ₁ is designed to heat the A side uniformly, it was confirmed in advance that the hardness was almost uniform over the entire surface, and therefore the above problem could not be solved. It was determined that the cause of the dots was due to the tempering process in the tempering zone TZ, and the following temperature measurement experiment was conducted.

Temperature measurement experiment (a) Specimen: Track link of bulldozer shown in Figure 2a l…197mm h…75mm w ₁ …15mm w ₂ …30mm (b) Experimental method: Tempering tube on the heat treatment line shown in Figure 1a Hardened specimen W 1 located at point R immediately before the entry side of frequency induction heating coil C ₂ , and hardened and tempered specimen W ₂ located at point S immediately before the exit side of frequency induction heating coil C ₂ .
and were taken from the line respectively, and the surface to be hardened A
The temperature was measured using a temperature indicator at multiple points on a line substantially along the longitudinal direction indicated by dotted lines in FIG. 2a.

C. Experimental results: The above temperature measurement values are plotted on a chart with temperature on the vertical axis and longitudinal measurement points on the horizontal axis, and the results are shown in Figure _2b for specimen W1 and Figure 2c.
The temperature characteristic curve of specimen _W2 was obtained.

Regarding the above temperature measurement experiment results, the present inventors:
Although the surface layer of specimen _W1 before tempering has been sufficiently hardened by rapid cooling after heating in the quenching zone QZ, it has a large heat capacity and a slow cooling rate due to the self-cooling phenomenon caused by air cooling. The temperature characteristic curve is Fig. 2b
As shown in Figure 2, it is considered that a temperature difference of approximately 80°C occurs between the Aa surface and the Ab surface, and this residual heat is added to the entire cross-sectional heating by the low frequency of the induction heating coil _C2 in the tempering zone TZ, and the specimen Although the temperature difference is not as large as that seen in W ₁ , it is quite large at 50℃.
This result is observed as the temperature characteristic curve of specimen W ₂ shown in Figure 2 c, where there is a temperature difference between It was determined that this resulted in a uniform hardened layer.

The present inventor made the invention described below based on the ideas and judgments derived from the above experimental results.

The gist of the present invention is to continuously feed a deformed material having portions with different cross-sectional areas in the longitudinal direction onto a conveying line including a hardening zone and a tempering zone, and to When surface-hardened irregular shaped materials are tempered by low-frequency induction heating in the tempering zone, heating coils of the length necessary to perform the specified tempering are divided into multiple parts and placed at specified intervals on the conveyance line. After passing through the low-frequency heating coil at the front of the conveyor line, only the hardened surface of the large cross-sectional area of the shaped material is forcedly cooled by spraying or air or gas for a predetermined period of time, and then A method for induction tempering of irregular shaped materials in a continuous heat treatment line, characterized in that the materials are introduced into a frequency heating coil.

The present invention will be explained according to an embodiment shown in FIG. 3a. Figure 3a is a partial front view of only the tempering zone TZ in the heat treatment line, and is a partial front view of only the tempering zone TZ in the heat treatment line.
The induction heating coil connected to C _2-a and C _2-b are divided into C 2-a and C 2-b and arranged along the conveyance line with a predetermined interval apart. The heating coils C _2-a and C _2-b are set to be able to heat the entire cross section of the profiled material W to a predetermined tempering temperature or to maintain the temperature for a predetermined time after raising the temperature by matching the length and the number of windings. In the middle of the conveyance line in which the heating coils C _2-a and C _2-b are arranged at a predetermined interval, a fluid jet nozzle 5 is installed on the surface to be hardened of the irregular shaped material W being conveyed on the conveyance line. It is placed with its hole facing A. The fluid injection nozzle 5 is connected via a solenoid valve V ₁ to, for example, a cooling water supply source P ₁ and a pressurized air supply source P ₂ , respectively, through pipes p ₁ and p ₂ .
and are connected to pipe _p3 where they are merged. pipe
The flow rates of both p ₁ and p ₂ can be adjusted using variable throttle valves, and a solenoid valve V ₂ is connected to pipe p ₂ .
is inserted. The electromagnetic valves V ₁ and V ₂ use known detection means to detect each Ab surface of each irregularly shaped material W being continuously conveyed on the chain belt 12 when it arrives directly below the fluid injection nozzle 5. It is configured to be opened and closed by a timer T which outputs an operation signal in response to a detection signal and maintains the output for a predetermined period of time (for example, 1 to 5 seconds) determined according to the transport speed of the transport device 1. Therefore, the fluid injection nozzle 5 can eject a mixture of cooling water and air, that is, a mist, the flow rate of which is adjusted according to the output of the timer T.

Tempering when heat-treating the deformed body W in the heat treatment line using the tempering zone TZ having the above configuration will be explained.

The irregular shaped material W, which has passed through the quenching zone QZ and whose A side has been uniformly quenched, reaches the low-frequency induction heating coil C _2-a in front of the conveyor line in the tempering zone TZ, and while passing through the heating coil C _2-a. As a result, the temperature of the Ab surface, which has a large residual heat during quenching, is raised to near the predetermined tempering temperature. Next, the irregularly shaped material W sequentially passes directly above the fluid spray nozzle 5, which starts spraying when the Ab surface arrives, and
This continues until the Ab plane passes. Therefore, the temperature of the Ab surface, which has been heated to near the predetermined tempering temperature, rapidly decreases to a temperature lower than that of the Aa surface. In addition, the mist sprayed onto the Ab surface will immediately evaporate as it comes into contact with the Ab surface, which has a temperature above the boiling point.
It will not run off as water onto surfaces or other sides.
As the chain belt 12 travels, the irregularly shaped material W is further moved to the low frequency induction heating coil C _2-b at the rear of the conveyor line.
sent within. While passing through the heating coil C _2-b , the deformed material W is heated again over its entire cross section, and the temperature of the Aa side of the quenched A side reaches almost the predetermined tempering temperature, and the temperature is lowered by spraying. The Ab surface, which has undergone this process, reaches approximately the predetermined tempering temperature by heat conduction from the deep part, which has a large heat capacity, and by induction heat generation. Thus, the hardened surface A of the irregularly shaped material W is
Both the Aa side and the Ab side are heated to the predetermined tempering temperature, and in this state are carried out from the tempering zone TZ.
The end of the chain belt 12 is discharged.

Figure 3b shows the tempering zone TZ where the present invention was implemented.
Immediately after the exit side of the heating coil C _2-b in Figure 1a
It is a temperature characteristic curve diagram created based on the measured values obtained in the same manner as the temperature measurement experiment described above for the irregularly shaped material W at point S in FIG. From the temperature characteristic curve diagram, it was confirmed that the method of the present invention sufficiently achieved the purpose of soaking tempering.

In the above embodiment, the induction heating coil for tempering is divided into two parts, but if necessary, it may be divided into three or four parts, and a spray device may be provided between each of the divided coils. The length, number of windings, and winding pitch of the divided heating coils may be determined depending on the difference in residual heat during quenching, the shape of the profiled material, the holding time at the tempering temperature, and other conditions.

In the above embodiment, the fluid jetted from the fluid jet nozzle 5 is a mist, but depending on the heating temperature difference, the shape of the irregularly shaped material, and other conditions, it is also possible to achieve a sufficient effect by jetting air; In some cases, it may be necessary to uniformly heat the ice cream by injecting carbon dioxide gas vaporized from the ice cream or the like to intensify the cooling effect.

Further, the fluid supply device to the fluid injection nozzle 5 is not limited to the above embodiment.

In Fig. 3a, the heating coils C _2-a and C _2-b are connected to the power supply.
Although it is connected in series to EL, it can also be connected in parallel.

In the above embodiment, only one hardened surface, side A, is used, but it goes without saying that the present invention is effective even when a plurality of surfaces are hardened.

By carrying out the tempering method according to the present invention, (1) it is possible to uniformly heat the hardened surface of the deformed material up to a predetermined tempering temperature in a continuous heat treatment line, resulting in uniform hardness without uneven tempering; It is possible to obtain a heat-treated product with a hardened layer.

(2) It is highly practical because it can be easily implemented without making extensive changes to the heat treatment line or relying on multiple expensive devices, and the effects obtained are extremely large.

[Brief explanation of drawings]

FIG. 1a is a partially sectional front view for explaining a conventional heat treatment line, FIGS. 1b and c are perspective views of a member to be heat treated in the heat treatment line of FIG.
Figure a is a plan view and a front view of the specimen used in the temperature measurement experiment when heat treated on the conventional heat treatment line shown in Figure 1 a, and Figures 2 b and c are before and after tempering, respectively, when using the conventional tempering equipment. A temperature characteristic curve diagram of the surface A of the specimen after tempering, FIG.
FIG. 3b is a temperature characteristic curve diagram immediately after tempering of the hardened surface A of the profiled material obtained using the apparatus shown in FIG. 3a. W...Deformed material, A...Hardened surface, Ab...Surface of large cross-sectional area, QZ...Hardened zone, C _2-a ,
C _2-b ...Low frequency induction addition.

Claims (1)

[Claims] 1 A deformed material having portions with different cross-sectional areas in the longitudinal direction was continuously fed onto a conveying line including a quenching zone and a tempering zone, and surface hardening was performed on a predetermined surface in the longitudinal direction in the quenching zone. In the case of tempering a deformed material by low-frequency induction heating in a tempering zone, a plurality of low-frequency heating coils each having a length necessary to perform a prescribed tempering are divided into multiple parts and arranged at prescribed intervals on a conveyance line, The shaped material that has passed through the low-frequency heating coil at the front of the conveyor line is forcedly cooled by spraying, air, or gas for a predetermined period of time only on the hardened surface of the large cross-sectional area of the shaped material, and then the low-frequency heating coil at the rear is applied. A method for induction tempering of deformed materials in a continuous heat treatment line, characterized in that the materials are fed into coils.