JP3187037B2 - Remelt curing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for remelting and curing a cam surface of a camshaft and the like.

(Prior Art) Conventionally, as a method of hardening a surface of a metal product such as a camshaft, for example, as disclosed in JP-A-58-196362, an energy beam is applied to a surface to be hardened (for example, a cam surface). A so-called re-melt hardening method is known in which the surface layer is locally re-melted by irradiation to chill the structure and increase its hardness.

(Problems to be Solved by the Invention) By the way, in order to obtain a deeper chill layer in such a re-melt hardening method, it is necessary to increase the output of the energy beam irradiating means. When the output is increased, the heat energy given to the work increases, but the cooling mass is constant, so that it takes time until the molten metal is cooled and solidified again. On the other hand, the metal melted by the beam irradiation flows due to an external action such as gravity or rotation of the work until the metal is solidified again.

Therefore, the longer the solidification time of the molten metal, the greater the flow due to external action, and in the state where the molten metal has solidified, deformation such as undulation occurs on the hardened surface of the work, and as a result, for example, the amount of this deformation If the finish grinding allowance is equal to or greater than the scheduled finish grinding allowance, the surface roughness of the surface to be cured cannot be secured.

Therefore, an object of the present invention is to propose a remelt hardening method capable of preventing deformation of a surface to be hardened after a remelt hardening process as much as possible.

(Means for Solving the Problems) In the present invention, as a specific means for solving such problems, an energy beam irradiating means for irradiating an energy beam to a surface to be hardened of a work is arranged to face each other, When performing the curing treatment by re-melting the surface to be cured while appropriately moving the energy beam irradiation means relative thereto, a magnetic coil is arranged on the outer peripheral side of the energy beam irradiation means, and 1.5 to 6.0 It is characterized in that beam irradiation is performed while passing an alternating current of Hz.

(Operation) Since the present invention has such a configuration, the following operation is obtained.

By irradiating the beam to the hardened surface of the work while applying an alternating current to the magnetic coil, the metal melted by the beam irradiation generates Lorentz force generated by the beam flow and the magnetic field, which are electron transfer phenomena. Received and agitated.

In this case, since an alternating current is passed through the magnetic coil, the direction of the Lorentz force acting on the molten metal changes alternately at the same cycle as the frequency of the alternating current, and the stirring action of the molten metal is further promoted. .

The molten metal is stirred by receiving Lorentz force until it solidifies, which promotes the dissipation of heat of fusion to the non-molten part of the work or the surrounding atmosphere, enabling solidification in a shorter time. Become.

Since the molten metal solidifies in a shorter time, chilling, that is, hardening is promoted, and deformation of the molten metal under the influence of gravity or the like is suppressed as much as possible.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a case where the remelt hardening method of the present invention is applied to a remelt hardening treatment of a cam surface 2a of a cam 2 of a camshaft 1. In FIG. A torch (corresponding to an energy beam irradiating means in the claims), and the beam torch 3 has its electrode 5 corresponding to the cam surface 2a (that is, the surface to be cured of the work in the claims). ) With a predetermined interval.

A magnetic coil 4 is provided outside the beam torch 3.
The magnetic coil 4 is supplied with an alternating current of a predetermined frequency from an alternating current power supply 6.

In this apparatus, the camshaft 1 is rotated around its axis (in the direction of arrow c), and the beam torch 3 is reciprocated (in the direction of arrow ab) in a direction perpendicular to the axial direction of the camshaft 1. The beam is emitted from the beam torch 3 to the cam surface 2a of the cam 2, and the cam surface 2a
Is re-melted. In FIG. 1, reference numeral 20 denotes a beam emitted from the beam torch 3, and reference numeral 21 denotes a beam irradiation locus on the cam 2a.

In the case of re-melting the cam surface 2a by this beam irradiation, in this embodiment, the present invention is applied as shown in FIG.

By doing so, the molten metal 7 near the cam surface 2a melted by the beam irradiation can emit the beam 22
The mixture is stirred by receiving Lorentz force generated by the magnetic field 23. In this case, since the alternating current is supplied to the magnetic coil 4, the direction of the Lorentz force changes alternately at the same cycle as the frequency of the alternating current, so that the stirring action is further promoted.

By stirring the molten metal 7 in this way, the heat energy dissipating property is enhanced as compared with the case where there is no stirring action. As a result, even when the output of the beam torch 3 is increased to obtain a deeper chill layer (that is, when the thermal energy of the molten metal 7 is large),
The molten metal 7 solidifies in a shorter time.

In addition, the fact that the molten metal 7 solidifies in a shorter time not only means that the chilling of the structure is promoted and its hardness performance is improved, but also that the molten metal 7 is subjected to an external action such as gravity during the processing operation. As a result, the deformation period is shortened, and the deformation of the cam surface 2a after solidification is prevented as much as possible. Therefore, the conventional disadvantage that the deformation amount becomes larger than the finish grinding allowance and defective products are generated is reliably prevented, and the product yield rate is improved accordingly.

However, even though the molten metal 7 is agitated by Lorentz force and its solidification is promoted, the direction of the Lorentz force changes depending on the frequency of the supplied alternating current, and therefore, the solidification promoting action due to the agitation. It is considered that also changes with the frequency of the alternating current.

The inventor of the present application has developed a magnetic coil in order to obtain a frequency at which the most effective stirring action is obtained, that is, a frequency at which the dent amount of the cam surface 2a after the re-melting process is small and a high chill hardness is obtained. The remelting treatment experiment was repeatedly performed while sequentially changing the frequency of the supply current to No. 4, and the results are summarized in FIG. 3 and FIG.

From the consideration of these experimental data, the AC current frequency was set to 1.5
It was found that when set in the range of -6.0 Hz, a cured surface excellent in both the dent amount and the chill hardness was obtained.

In the frequency range where the frequency is 1.5 Hz or less, the remelting hardening performance deteriorates because, in this frequency range, the change in the direction of the Lorentz force is small and the movement of the molten metal is slow. Is considered to be due to inferiority.

Conversely, the decrease in remelt hardening performance in the frequency range above 6.0 Hz is because the Lorentz force changes drastically in this frequency range, hindering the movement of the molten metal and consequently the magnetic properties. It is considered that only the same degree of heat dissipation as in the case without stirring was obtained.

Therefore, from the above experimental results and considerations, from the viewpoint of ensuring smoothness and hardness performance of the surface to be cured,
It can be said that the frequency of the current supplied to the magnetic coil 4 should be set in a frequency range of 1.5 to 6.0 Hz. This is the reason that the present invention limits the frequency of the alternating current supplied to the magnetic coil 4 to a range of 1.5 to 6.0 in the claims.

(Effects of the Invention) As described above, according to the present invention, the beam irradiation on the surface of the workpiece to be cured is performed by the magnetic coil 4 at the frequency of 1.
By performing the process while applying an alternating current of 5 to 6.0 Hz, deformation of the surface to be hardened after remelting and hardening can be prevented most effectively, which has the effect of contributing to an improvement in product yield. It is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a remelting and curing method according to an embodiment of the present invention, FIG. 2 is an explanatory view of a remelting state by beam irradiation, and FIG. FIG. 4 is a chill hardness characteristic diagram of the surface to be cured with respect to the AC current frequency. DESCRIPTION OF SYMBOLS 1 ... Camshaft 2 ... Cam 3 ... Beam torch 4 ... Magnetic coil 5 ... Electrode 6 ... AC power supply 7 ... Molten metal 20 ... Beam 21 ... Beam irradiation locus 22 ... Beam flow 23 ……magnetic field

Claims (1)

(57) [Claims] An energy beam irradiating means for irradiating an energy beam to a surface to be hardened of a workpiece is disposed opposite to the workpiece. When performing the curing treatment by melting, a magnetic coil is arranged on the outer peripheral side of the energy beam irradiation means, and 1.5 to 6.0
A re-melt hardening method characterized by performing beam irradiation while passing an alternating current of Hz.