JPH03180428A - Method for quench hardening sheet metal member - Google Patents

Abstract

PURPOSE:To minimize the occurrence of quenching distortion by interposing a couple of opposed piece parts of a sheet metal member between an inner die and outer dies and carrying out, at time intervals, cooling by means of passing a coolant through passages in the dies and cooling applied to the noncontact part between the dies and the member. CONSTITUTION:A couple of opposed piece parts 1a, 1b of a sheet metal member 1 heated up to a hardening temp. is interposed between an inner die 4 and outer dies 5, 6. A coolant is supplied into a coolant passage 13 in the inner die 4, by which respective central parts of the inner side faces of the opposed piece parts 1a, 1b are locally quenched. Successively, the coolant is supplied into respective coolant passages 14, 15 of the outer dies 5, 6, by which respective central parts of the outer side faces of the opposed piece parts 1a, 1b are locally quenched. Finally, the coolant is sprayed through spray holes 26 of a cooling ring 25, by which the noncontact part between the dies 4, 5, 6 and the sheet metal member 1 is quenched down to the ordinary temp. By performing the above coolings at time intervals, coolings for hardening are carried out while changing cooling velocities in respective parts.

Description

[Detailed Description of the Invention] L Industrial Application Field The present invention relates to a method for quenching and cooling an IIN member in which a longitudinal thin steel plate is shaped into a U-shaped or O-shaped bottom. More specifically, after heating a pair of opposing pieces of a U-shaped or O-shaped thin plate member, both sides of the thin plate member are sandwiched between molds and quenched and cooled. The present invention relates to a method for quenching and cooling thin plate members.

b. Prior Art This type of thin plate member is used as a part of an equi-articulated universal joint such as a tripod joint installed in the drive system of a front-wheel drive vehicle. As shown in FIG. 6, the thin plate member 30 is usually bent into a U-shape or a U-shape, and has two opposing pieces 30a, 30a and 30a, respectively.
30b is subjected to hardening treatment.

By the way, when hardening the thin plate member 30, first the pair of opposing pieces 30a and 30b of the thin plate member 30 are heated to a required hardening temperature, and then the pair of opposing pieces 30a and 30b are heated as shown in FIGS. 6 and 7. Inner mold 31 is inserted between 30a and 30b, and outer molds 32 and 33 are respectively arranged on the outside of opposing pieces 30a and 30b, and the opposing pieces are pressed with a pressing force F that does not cause plastic deformation of thin plate member 3o. Parts 30a, 30b
are sandwiched between the inner mold 31 and the outer mold 32 and 33, respectively. Then, the inner mold 31 and the outer mold 32
, 33 are respectively formed inside the cooling liquid passages 34°3.
5 and 36 at the same time, thereby quenching and cooling the thin plate member 30, which is the object to be quenched.

Problems to be Solved by the C0 Invention However, the above-mentioned conventional method has the following problems.

That is, the opposing piece portion 30a of the thin plate member 30 (hardened material)
, 30b (necessary hardening location) but also the entire thin plate member 3° is heated, or the opposing piece 30
In any case where only parts a and 30b are partially heated, the opposing pieces 30a and 30b contract in the range from the quenching temperature to the martensitic transformation start temperature during quenching and cooling, and the martensitic transformation starts. Although it expands again in the range from the temperature to the end temperature of martensitic transformation, it is difficult to control the contraction rate and expansion rate at this time. In other words, if the thin plate member 3o is cooled while being clamped with a pressing force that does not cause plastic deformation, it is not possible to locally change the cooling rate at various parts of the thin plate member 3o, so that the problem that occurs during quenching cooling cannot be achieved. There was a major problem in that deformation caused by contraction and expansion of the thin plate member 3o due to thermal stress and martensitic transformation stress could not be suppressed. Therefore, the actual situation is that in the past, a fairly large quenching strain occurs.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to minimize the occurrence of hardening distortion when hardening a pair of opposing pieces of a thin plate member as described above. It is an object of the present invention to provide a quenching cooling method that can reduce the amount of quenching.

d. Means for Solving the Problems In order to achieve the above-mentioned object, in the present invention, after heating a pair of opposing pieces of a U-shaped or U-shaped thin plate member, the pair of opposing pieces are heated. In a method for quenching and cooling a thin plate member in which the pieces are respectively inserted between molds and quenched and cooled, (A) a pair of opposing pieces of the thin plate member heated to a predetermined quenching temperature; An inner mold is placed in between, and an outer mold is placed outside of the inner mold, and each of the pair of opposing pieces is sandwiched between the inner mold and the outer mold with a required pressure. (B) cooling the pair of opposing pieces by supplying a cooling liquid to a cooling liquid passage provided in the inner mold; Second
(C) a third cooling step of cooling the pair of opposing pieces by supplying a cooling liquid to cooling liquid passages provided in each of the outer molds; (D) a third cooling step of cooling the pair of opposing pieces; By spouting a cooling liquid from a jacket arranged at intervals with respect to the mold, the outer mold, and the thin plate member, a non-contact portion between the inner mold, the outer mold, and the thin plate member is cooled. By performing the fourth cooling step and the following at time intervals, the cooling rate at each portion of the pair of opposing pieces to be quenched and cooled is varied.

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 5.

Fig. 1 shows a quenching cooling device 2 used for quenching and cooling a thin plate member l.As shown in Fig. 1, this device 2 is fixed at a predetermined location on the device base 3. A disposed inner mold 4, a pair of outer molds 5 and 6 and a positioning jig 7, each movably disposed with respect to the inner mold 4,
A hydraulic cylinder 8 presses and drives these members 5, 6.7.
．． 9°lO. Furthermore, as shown in FIGS. 3 and 4, the inner mold 4. A cooling liquid injection jacket (cooling ring) 25 is provided above the outer mold 5.6 and the positioning jig 7. In addition, in Figure 1, 1
1.12 is a guide mechanism for the outer mold 5.6.

As clearly shown in FIG. 2, the above-mentioned inner mold 4 is formed by integrally forming a tapered trapezoidal part 4b at the tip of a rectangular parallelepiped main body part 4a. A cooling liquid passage 13 is formed in the central portion of the cooling liquid in the height direction. The coolant passage 13 is formed by a pair of grooves 13a and 13b that are opened at the base end surface 4C of the inner mold 4 and are opened along approximately half of the longitudinal direction at the central portion of the side surfaces 4d+4e.
and communication paths 13c and 13d for communicating these grooves 13a and 13b with each other.

On the other hand, the above-mentioned outer mold 5.6 has a rectangular parallelepiped bottom, and cooling liquid passages 14 and 15 are provided on one side of the mold, respectively. These coolant passages 14, 15 are formed by grooves 14a and 15a formed in half of the -side surface, and grooves 14
It is composed of passages 14b and 15b that are connected to passages 14b and 15a. Coolant supply pipes 1B and 19.20 are arranged on the upper surfaces of the inner mold 4 and the outer mold 5.6,
The cooling liquid passage 13 is connected through these pipes 18 to 20.
．． Cooling liquid is supplied to 14 and 15, respectively.

Further, the above-mentioned positioning jig 7 has a trapezoidal notch 21, and a pair of tapered surfaces 21a of this notch 21,
The intermediate portion of the thin plate member 21b is brought into line contact with the bent portion of the thin plate member l.

Further, as shown in FIGS. 3 and 4, the above-mentioned cooling ring 25 is fixed to the upper part of the inner mold 4 and the outer molds 5 and 6 at a predetermined interval, and is fixed to the bottom wall of the cooling ring 25. A large number of coolant injection holes 26 are formed at regular intervals, and a coolant supply pipe 27 is connected to the upper wall thereof.

Next, the operation and effect when the U-shaped thin plate member l is quenched and cooled using the quenching cooling device 2 having the above-described configuration will be explained.

First, the pair of opposing pieces 1a and lb to be hardened of the U-shaped thin plate member 1 that has been subjected to carburizing and cooling treatment is heated to the required hardening temperature using a high-frequency induction heating coil or the like, and then the thin plate member is heated. The opening side portion of l is fitted into the inner mold 4. Next, the positioning jig 7 is driven by operating the hydraulic cylinder lO, and the tapered surfaces 21a and 21b of the positioning jig are bent into a pair of thin plate members l. 1, and press the thin plate member l in the direction of the arrow in FIG. As a result, the intermediate portion of the thin plate member l is
Surface 21a.

21b and the tip surface of the trapezoidal part 4b of the inner mold 4, and the inner surfaces of the pair of opposing pieces 1a, lb are arranged corresponding to the side surfaces 4d, 4e of the inner mold 4.

After the thin plate member 1 is positioned and attached to the inner mold 4 in this manner, the pair of outer molds 5 and 6 are moved to the arrow B in FIG. 1 by operating the hydraulic cylinder 8.9.
direction and the direction of arrow C to sandwich the pair of opposing pieces 1a and lb of the thin plate member 1 between the inner mold 4 and the outer mold 5.6. Along with this, the thin plate member l has an inner mold 4,
They are held in predetermined positions by the outer molds 5, 6 and the positioning jig 7, and the inner mold 4 and the outer mold 5.6 are tightly attached to the pair of opposing pieces 1a+lb. As a result, the heated opposed pieces 1a, lb are first cooled down by close contact with the inner mold 4 and the outer mold 5.6 (cooling step in FIG. 1).

Next, the coolant is supplied to the coolant passage 13 of the inner mold 4 via the pipe 18 . Along with this, the cooling liquid flows into the passage 1.
3, so that a predetermined location of the thin plate member 1, that is, the central location of the inner surface of the portion to be hardened of the pair of opposing pieces 1a and lb, is locally rapidly cooled (second cooling step). The cooling liquid that has flowed through is discharged to the outside of the inner mold 4 and guided to the outside of the apparatus through a predetermined drainage path.

Following this, a cooling liquid is supplied via the pipe 19.20 to the cooling liquid channel 14.15 of the outer mold 5.6.

Accordingly, since the cooling liquid flows into the passage 14.15, the predetermined portions of the thin plate member l, that is, the pair of opposing pieces 1a,
The central part of the outer surface of the part to be hardened in Ib is locally rapidly cooled (third cooling step), and the passage 14
．． The cooling liquid that has flowed through the mold 15 is discharged to the outside of the outer mold 5.6 and guided to the outside of the apparatus through a predetermined drainage path.

Finally, as shown in Figures 3 and 4, the cooling ring 2
A cooling liquid is injected from the injection holes 26 of No. 5 to rapidly cool the non-contact portions of the inner mold 4, outer molds 5 and 6, and the thin plate member 1 to room temperature with the cooling liquid (fourth cooling step).

As described above, when quenching and cooling the pair of opposing pieces 1a and lb of the FI plate member 1, which is the object to be hardened, each part of the opposing pieces 1a and lb is cooled at a time interval (time lag). The quenching process is completed by quenching and cooling the parts at different cooling rates.

As described above, in this example, since the cooling rate at each part of the thin plate member l, which is the object to be hardened, is controlled, the magnitude of the thermal stress generated at each part of the part to be hardened is made to be different. Since the start timing of martensitic transformation is made different at each location, the amount of contraction and expansion of the thin plate member 1 can be controlled. That is, the cooling rate is slowed to reduce thermal stress and transformation stress in areas that are likely to shrink, thereby making it possible to locally adjust the shrinkage rate. On the other hand, in areas that are prone to expansion, the cooling rate is increased to reduce thermal stress.
It is possible to increase the transformation stress and thereby locally adjust the expansion rate. In other words, it is possible to cause changes in the start and end points of shrinkage and the start and end points of transformation of each portion of the pair of opposing pieces 1a and 1b of the thin plate member 1, and as a result, the occurrence of quenching strain can be reduced. It is possible to make a minimum impression.

A specific example of implementing the quenching cooling method according to the present invention will be described below.

(1) Material of thin plate member: 5Cr420 (Carburized cooling treatment) (2) Dimensions of yI plate member (a) Total length = 70cm Cbl Plate width: 13.40cm (C) Plate thickness: 5. OM (d) Width of opposing pieces Length between outer surfaces: 43.77 to 43.82 Length between inner surfaces: 33.77 to 33.82 m (3) Cooling conditions (a) Mold press pressure 0)) Pressing time: 11 seconds (C) Coolant New Conquenchant A (d)
Coolant flow rate Inner mold 2827 in Outer mold: 5 jM'++ in Cooling ring: 10 j! /maro1n (e) Time interval (time lag) (i) Time interval from the end of the first cooling process to the start of the second cooling process: 1.5 seconds.

(11) Time interval from the end of the second cooling process to the start of the third cooling process: 0.5 seconds.

(f) Cooling time: 10 seconds in each of the first to fourth cooling steps. The cross-sectional hardness of the quenched portion of the thin plate member obtained by quenching and cooling under the above conditions was measured using a Vickers hardness tester. The results shown in FIG. 5 were obtained. As is clear from the measurement results shown in Figure 5, the quenched surface has been sufficiently hardened up to the carburized layer, and the outermost surface hardness is H1820.
shows the value of

Further, the internal hardness shows a value of H□470 to 490, and these values show the quenching hardness of the material 5Cr420.

In addition, when strain was measured using a dial gauge at 10 pieces and the measurement position was 10,20,30,40,50 points from the opening end of the thin plate member, the measurement results as shown in the table below were obtained. Ta. Note that the measured values shown in the table indicate the magnitude of distortion with respect to the finished standard dimensions (33, 92).

As is clear from this table, the finished dimensions were 33.92±0.1- at each location, and it was confirmed that all locations were within the required dimensions and that only extremely small distortions occurred.

Although one embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above, and various modifications can be made based on the technical idea of the present invention.

For example, in the embodiments described above, the inside of the pair of opposing pieces 1a and 1b of the thin plate member 1 is cooled and then the outside thereof is cooled, but this may be done in the opposite manner. The present invention can be applied not only to a U-shaped thin plate member but also to a U-shaped thin plate member.

e. Effects of the Invention As described above, the present invention is designed to change the cooling rate in each part of the U-shaped or U-shaped thin plate member that is the object to be hardened, so that the parts that are likely to shrink are The cooling rate is slowed down to reduce thermal stress and transformation stress, while the cooling rate is increased to increase thermal stress and transformation stress in areas that are likely to expand. The contraction speed and expansion speed can be controlled, that is, the contraction start and end points and the expansion start and end points in each part can be adjusted, and quenching distortion can be suppressed to the minimum dust.

[Brief explanation of drawings]

1 to 5 are for explaining one embodiment of the present invention, and FIG. 1 is a plan view of a quenching cooling device for carrying out the quenching cooling method according to the present invention, and FIG. Fig. 2 is a perspective view showing a thin plate member held between molds, Fig. 3 is a sectional view taken along the line ■-■ in Fig. 2, and Fig. 4 is a cross-sectional view taken along the line IV-- in Fig. 2.
5 is a graph showing the measurement results of the cross-sectional hardness of the opposing piece (quenched part) of the thin plate member, and FIGS. 6 and 7 are for explaining the conventional quenching cooling method. FIG. 6 is a perspective view showing a thin plate member held between molds, and FIG. 7 is a plan view of the same. 1... Thin plate member which is the object to be quenched, la, lb... Opposing piece part, 2... Quenching cooling device,
4...Inner mold, 5.6...Outer mold, 7...
Positioning jig, 8.9.10... Hydraulic series 13, 14
．． 15...Cooling fluid passage. Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] After heating a pair of opposing pieces of a U-shaped or U-shaped thin plate member, the pair of opposing pieces are respectively sandwiched between molds and quenched and cooled. In the method for quenching and cooling a thin plate member, (A) an inner mold is disposed between a pair of opposing pieces of the thin plate member heated to a predetermined quenching temperature, and an outer mold is placed outside the inner mold. a first cooling step of cooling the pair of opposing pieces by respectively arranging them and inserting each of the pair of opposing pieces between the inner mold and the outer mold with a required pressure; (B) a second cooling liquid for cooling the pair of opposing pieces by supplying a cooling liquid to a cooling liquid passage provided in the inner mold;
(C) a third cooling step of cooling the pair of opposing pieces by supplying a cooling liquid to cooling liquid passages provided in each of the outer molds; (D) a third cooling step of cooling the pair of opposing pieces; By spouting a cooling liquid from a jacket arranged at intervals with respect to the mold, the outer mold, and the thin plate member, a non-contact portion between the inner mold, the outer mold, and the thin plate member is cooled. Quenching of a thin plate member, characterized in that the cooling rate at each part of the pair of opposing pieces to be quenched and cooled is changed by performing the fourth cooling step and the following at time intervals. Cooling method.