JPH0227410B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to an induction hardening method, and more specifically, in order to obtain a continuous hardened layer on the teeth of a large rack, the hardened portion is placed between the contacts of an induction coil that are in contact at both ends. The large rack is placed in the rack and heated by passing a high frequency current through it, and then the large rack is immersed in a cooling liquid to cool it down, and the cooling liquid is also applied to the rack part, which is the heated part, and the back part, which is the non-heated part, of the large rack. This invention relates to a method for energizing induction hardening of large racks in which cooling is performed by injection. Conventional Technology Conventionally, the strength of the tooth tips, tooth bottoms, and tooth surfaces of large racks has been increased by ion nitriding or the like. Problems to be Solved by the Invention However, large racks are often used under heavy loads, and the above method has a shallow hardening depth, resulting in a very short service life. Therefore, an induction hardening method was adopted, but if many tooth tips, tooth bottoms, and tooth surfaces were induction hardened at once, distortion such as deformation or bending of the large rack would occur, so a method of moving hardening one tooth at a time was adopted. However, because a discontinuous area of the hardened layer was formed at the tooth tip or tooth bottom, satisfactory strength could not be obtained. The present invention has been made in view of the above,
The object of the present invention is to provide a method by which a continuous hardened layer can be obtained over the entire tooth of a large rack, including the tooth tip, tooth bottom, and tooth surface. Means for Solving the Problems The method of current induction hardening of a large rack according to the present invention is such that induction coils are installed at both ends of the rack portion including the tooth tips, tooth bottoms and tooth surfaces, which are the hardened portions of the large rack. A method of hardening the induction coil and the rack by applying a high-frequency current to the induction coil and the rack part by bringing the installed contacts into contact with each other. The large rack is closely attached so as to cover the unhardened parts of the upper and lower surfaces of the large rack, and after preheating and heating with the high frequency current, the large rack is immersed in the coolant in the coolant tank. However, the gist is that the cooling liquid is also injected into the heated part of the large rack, which is the heated part, and the back part, which is the unheated part, in the liquid. Action When the contacts placed at both ends of the induction coil are brought into contact with both ends of the easy part and a high frequency current is applied to the induction coil, the high frequency current flowing from the contacts and the electromagnetic current of the induction coil will flow into the easy part. A cumulative high-frequency current flows together with the induced high-frequency current generated by the induction effect, and the rack portion including the tooth tip, tooth bottom, and tooth surface is heated. Next, the large rack is immersed in the cooling liquid in the cooling liquid tank provided below, and in this state, the cooling liquid is also applied to the rack part, which is the heated part, and the back part, which is the unheated part, of the large rack. Injected. Embodiment FIG. 1a is a plan view showing an embodiment of the present invention.
FIG. 1b is a sectional view taken along the line AA in FIG. 1a, and FIG. 2 is a sectional view showing a large rack immersed in a coolant tank and injecting coolant. In FIG. 1a, a large rack 1, which is a metal workpiece, is held by a holding device (not shown) so that the tooth top surface is in a vertical plane. 2b and a tooth surface 2c. The induction coil 10 includes a coil portion 11, conductor portions 12a, 12b, a pair of contacts 13a, 13b, and an insulator 14, all of which are made of a highly conductive metal. The coil portion 11 having a substantially rectangular cross section is connected to the easy portion 2.
The rack part 2 is arranged at an appropriate distance from the rack part 2 so as to face the rack part 2. At one end of the coil part 11,
A conductor portion 12a having a substantially rectangular cross section and integral with the coil portion 11 is formed to protrude in a direction substantially perpendicular to the coil portion 11, and a contact 13a is fixed to the other end by brazing or the like. . The conductor portion 12b, which has a substantially rectangular cross section, is mounted oppositely to the conductor portion 12a with an insulator 14 interposed therebetween.At one end of the conductor portion 12b near the large rack 1, a contact 13b forming a pair with the contact 13a is provided. It is fixed by brazing etc. That is, the pair of contacts 13a and 13b are arranged at both ends of the induction coil 10. The contacts 13a and 13b are brought into contact with both ends of the rack part 2 by the pressing force of pneumatic or hydraulic clamps 21a and 21b, respectively. A high frequency current is supplied from a high frequency power source 40 to the conductor portions 12a and 13b. Reference numeral 3 denotes a rear portion of the large rack 1 that faces the rack portion 2. Blocks 15a and 15b, which are made of metal and have a substantially L-shaped cross section, are closely attached to the upper surface 4 and lower surface 5 of the large rack 1, respectively. Specifically, the block 15a is the unhardened portion of the large rack 1, that is, the upper surface 4 of the large rack 1.
In this case, it covers a portion from a portion a little distance away from the tooth bottom 2b to the back surface portion 3, and the upper end portion of the back surface portion 3, which is also a non-hardened portion. Further, the block 15b is similar to the upper block 15a, as shown in FIG. A coolant tank 30 containing a coolant 33 is provided below the large rack 1. A front cooling jacket 31 and a back cooling jacket 32 are disposed within the cooling fluid 33. The large rack 1 on which the blocks 15a and 15b are mounted is supported by a large rack support member 22 that is in contact with the lower surface of the block 15b.
This large rack support member is pneumatically or hydraulically displaced upwardly from the cylinder 24 and is secured to the upper end of the rod 23 which passes through the bottom surface of the coolant tank 30 and the coolant 33. Although not shown, the coil section 11 and the conductor sections 12a and 12b are equipped with metal pipes for the passage of coolant, and the contacts 13a and 13b are provided with holes for the passage of the coolant. It is being Next, the operation of this embodiment will be explained. A high frequency current is supplied from the high frequency power source 40 to the conductor portion 12a.
When power is applied to the coil portion 11 and the rack portion 2, a high frequency current flows through the coil portion 11 and the rack portion 2. That is, due to the high frequency current flowing through the path of the conductor portion 12a, the coil portion 11, the contact 13a, the rack portion 2, the contact 13b, and the conductor portion 12a, and the electromagnetic induction effect of this high frequency current flowing through the coil portion 11. The high frequency current generated in the rack part 2 and the induced high frequency current flow into the rack part 2, and the rack part 2 is heated. At this time, heating and air cooling are repeated several times using low power at first, until the heating temperature at the tooth tip and tooth bottom reaches the same level.
After the temperature difference is approximately 50° C. or less below the Ar ₃ transformation point, the power is increased to perform final heating and continue heating until the surface temperature becomes appropriate. This results in
The temperature difference between the tooth tip and the tooth bottom is small. After heating, the air pressure or oil pressure of the cylinder 24 is released, the rod 23 is lowered as shown in FIG. 2, and the large rack 1 is immersed in the cooling liquid 33.
Next, in this state, the cooling liquid 33 is injected from the front cooling jacket 31 and the rear cooling jacket 32 into the rack part 2 and the rear part 3 in the form of jets 35 and 36, respectively. Even in these cases, blocks 15a and 15 of large rack 1
The cooling of the portion covered by b is relaxed and has the effect of limiting the depth of the hardened layer on both end faces. In addition, since cooling is performed not only on the easy part 2 but also on the back part 3, which is a non-hardened part, the front cooling jacket 31
By appropriately adjusting the amount of cooling liquid injected from the back cooling jacket 32, the warping (bending) of the large rack 1 can be minimized. Therefore, distortions such as deformation and bending of the large rack 1 are extremely small, and the tooth tips, tooth bottoms, and tooth surfaces can be appropriately heated and cooled to obtain a uniform hardened layer. The heating and cooling conditions and specific numerical values of the results in this example are shown below. The steel type is
For SCM440, the main dimensions of the rack are module 1
2. Number of teeth is 28, tooth width is 160mm. Heating conditions (frequency 10kHz) Preheating: Power 50kW Repeat on/off until the tooth tip and tooth bottom reach 400±10℃. The total time required for this period is approximately 16 minutes. Heating: Electric power 200kW Time: 90 seconds Cooling conditions Refrigerant: Plastic quench 10%, 30℃ Cooling delay time: 18 seconds Easy partial injection amount: 700/min, (at a pressure of 5Kg/ ^cm2 ) Rear partial injection amount: 1200/min (at a pressure of 15Kg/ ^cm2 ) Results Hardening depth: Approximately 2-3mm from the tooth bottom Surface hardness: (320±10℃ x 3 hours of tempering) Tooth tip: Hs60~63 Tooth base: Hs60~ 65

[Table] Effects of the Invention As explained above, according to the method for induction hardening of large racks of the present invention, a high-frequency current is applied to the induction coil and the rack portion, and the high-frequency current flowing to the rack portion and the high-frequency current flowing to the coil portion are separated. Combined with the induced high-frequency current generated in the rack part due to the electromagnetic induction effect of the current, the rack part is induction hardened by the cumulative high-frequency current, and the tooth tip of the large rack is held in a vertical plane to form a thick plate. A metal block is closely attached to cover the unhardened parts of the upper and lower surfaces of the large rack, and after preheating and main heating are performed by electric induction hardening, the large rack is cooled in the coolant tank installed below it. Since the rack is immersed in the liquid and the cooling liquid is sprayed to the rack and rear surface in this state, the large rack is not deformed or bent, and the tooth tip, tooth bottom, and tooth surface are uniformly hardened. You can get layers.

[Brief explanation of drawings]

FIG. 1a is a plan view showing an embodiment of the present invention.
FIG. 1b is a sectional view taken along the line AA in FIG. 1a, and FIG. 2 is a sectional view showing a large rack immersed in a coolant tank and injecting coolant. 1...Large rack, 2...Rack part, 2a...
...Tooth tip, 2b...Tooth bottom, 2c...Tooth surface, 3...Back surface, 4...Top surface, 5...Bottom surface, 10...Induction coil, 11...Coil part, 12a, 12b...
Conductor part, 13a, 13b...Contactor, 15a, 1
5b...Block, 30...Cooling liquid tank, 31
...Front cooling jacket, 32...Back cooling jacket, 33...Cooling liquid.

Claims (1)

[Claims] 1 Contactors installed at both ends of the induction coil are brought into contact with both ends of the rack portion of the large rack, including the tooth tips, tooth bottoms, and tooth surfaces, which are the parts to be hardened, and a high-frequency current is applied to the induction coil and the rack. A method of quenching the parts by energizing them, the tooth tips of the large rack are held in a vertical plane, and a thick metal block is placed so as to cover the unhardened parts of the upper and lower surfaces of the large rack. After the large rack is mounted closely and preheated and heated by the high-frequency current, the large rack is immersed in a cooling liquid in a cooling liquid tank, and the heated and non-heated parts of the large rack are submerged in the liquid. This is an electric induction hardening method for large racks, which is characterized by injecting a cooling liquid also to the back surface.