JPH036320A - Production of parts subjected to remelting and hardening treatment - Google Patents

Abstract

PURPOSE:To prevent the generation of the surface ruggedness and shoulder shear droop of the above parts with the simple method by generating slight oscillation in the remolten pool formed by irradiation of high-density energy at the time of subjecting the parts to be treated to the remelting and hardening treatment by the above mentioned irradiation. CONSTITUTION:The part to be treated, for example, a cam shaft 1 is roughly worked and the surface of the cam part 1a thereof is ground to 4mu surface roughness. After this cam shaft 1 is preheated to 300 deg.C, the cam part 1a is subjected to the remelting treatment by using a TIG arc torch 2 and simultaneously, the shaft part 1b is excited by a vibrator 3. The surface of the cam part 1a is partially remelted by the heat of the generated discharge arc 4, by which a remolten pool 5 is formed; thereafter, the surface hardened layer is formed by the rapid self-cooling. The decreased surface tension of the pool 5, the accelerated generation of crystal nuclei and improved heat radiatability are obtd. by the above-mentioned excitation at this time, by which the purposes are attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing parts that are remelted and hardened by irradiation with high-density energy such as a laser beam, TIG arc, plasma arc, or electron beam. It is something.

(Prior art) In recent years, there has been a growing trend toward higher output in automobile engines, and as a result, for example, the cam surface, which is the sliding part of the camshaft that makes up the engine valve mechanism, are subject to higher surface pressure. Therefore, it is becoming essential to improve the wear resistance of the sliding portion. For this reason, a hardened surface layer has been formed on the sliding portion of a sliding member such as a camshaft.

One of the methods for forming the above-mentioned surface hardening layer is a method of remelting and hardening the desired sliding area by irradiating it with high-density energy such as a laser beam, TIG arc, plasma arc, or electron beam. For example, see Japanese Patent Laid-Open No. 61-270340).

(Problem to be Solved by the Invention) By the way, the formation of a hardened surface layer by high-density energy irradiation as described above is performed on the surface of a sliding part while slowly rotating the target part (for example, a camshaft). This is usually carried out by moving the high-density energy irradiation device to reciprocate and scan the irradiated area with high-density energy relative to the sliding area of the target part in the l] direction.

However, when forming a surface hardening layer by the method described above, a remelting pool is formed on the metal surface due to rapid high-density energy irradiation. "Waviness" and "waviness" are likely to occur on the surface, and if the hardened surface layer is formed in this state, unevenness may be formed on the hardened surface layer, and the edges of the sliding parts may be melted too much, resulting in shoulders. If the surface hardened layer is formed in this way, the polishing method used during the polishing process after formation may be too thick (as a result, only a shallow surface hardened layer is formed, or the surface hardened layer may sag). The lack of thickness in the portion limits the length of contact with the mating member, causing abnormal wear due to increased surface pressure.

In order to deal with the above-mentioned problems, in the above-mentioned known example (namely, Japanese Patent Laid-Open No. 61-270340), a roller or the like applies a pressing force to the part that has been remelted by high-density energy irradiation, and the surface of the part is efforts are being made to flatten the surface. However, when using the method of the above-mentioned known example, a complicated device is required as a means for applying a pressing force to the remelted portion, and problems remain in workability when applying the pressing force.

The present invention has been made in view of the above points, and an object of the present invention is to eliminate surface irregularities and shoulder sag in remelted and hardened parts using an extremely simple method.

(Method for Solving the Problems) In the present invention, as a method for solving the above problems, the high-density Microvibrations are caused in the remelting pool generated by the irradiation of density energy.

(Function) In the present invention, the following effects can be obtained by the above method.

That is, by causing minute vibrations in the remelting pool generated by irradiation with high-density energy, it is possible to reduce the surface tension of the remelting pool, promote crystallization nucleation, and improve heat dissipation. This speeds up the solidification of the remelt pool.

(Effects of the Invention) According to the method of the present invention, when the surface of the target processing part is irradiated with high-density energy to re-melt and harden the part, a re-melt pool is generated by the irradiation with the high-density energy. Since micro vibrations are generated in the remelt pool, it is possible to reduce the surface tension of the remelt pool, promote the generation of crystallization nuclei, and improve heat dissipation.As a result, the solidification of the remelt pool is accelerated and the formation This has the excellent effect of preventing the occurrence of unevenness and shoulder sag in the hardened surface layer by an extremely simple means.

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

Example 1 C: 3.5% by weight, Si: 2.0% by weight, Mn: 0.6
Weight%, P: 0.07% by weight, S: 0.03% by weight, C
rho, 06% by weight, Mg: 0.02% by weight, Fe,
A cam/yant 1 as shown in FIG. 1 was machined using alloyed cast iron having the composition of the remainder, and the surface of the cam portion 1a of the camshaft 1 was ground to a surface roughness of 4 μm. In other words, in this embodiment, the camshaft 1 is employed as the target component to be subjected to the remelting and hardening treatment.

Next, after preheating the camshaft 1 to 300°C, the cam portion 1a is remelted using a TIG arc torch 2, and at the same time, the shaft portion 1b of the cam/yant 1 is heated.
was excited by vibrator pen 3. The excitation level at this time was vibration acceleration of 1 m/5ec2, and the remelting conditions were: workpiece rotation speed, 065 rpm, and oscillation width:
6mm, on-rate rotation, 50 times/min, current value:
It was 65-85A.

As described above (when remelting the cam portion 1a of the camshaft 1 using the TIG arc torch 2, the heat of the discharge arc 4 generated between the TIG arc torch 2 and the cam portion 1a causes The surface of the portion 1a is partially remelted to form a remelting pool 5 (see Figure 2), and then self-quenched by the heat capacity of the cam shirts 1 to 1 themselves to form a surface hardening layer. However, in the case of this embodiment, since the cam shirt l-1 is vibrated by the vibrator pen 3 during the remelting process, slight vibrations are generated in the remelting pool 5. As a result, the surface tension of the remelting pool 5 is reduced, the generation of crystallization nuclei is promoted, and the heat dissipation properties are improved.As a result, the solidification of the remelting pool 5 is accelerated, and the formed surface hardening layer is improved. This will prevent the occurrence of unevenness and shoulder sag.Incidentally, in the case of this example, the surface roughness of the cam portion 1a after the remelting and hardening treatment is 5 μm (see Fig. 3), and the cam portion There was also no shoulder sagging at the end of 1a.

Example 2 ``1'' The same camshaft 1 as in Example 1 was used as the target processing part, and only the excitation level by the pie break pen 3 was changed to the vibration acceleration +3. Change to in/5ee2,
When the remelting and hardening treatment was performed under the same remelting conditions as in Example 1, the surface roughness of the cam portion 1a after the remelting and hardening treatment was 9 μm (see Fig. 3), and the end portion of the cam portion 1a was No shoulder sagging occurred.

Comparative Example 1 The same Kamunyaft 1 as in Example 1 was used as the target processing part, and no vibration was applied using the pie break pen 3.
When the remelting and hardening treatment was performed under the same remelting conditions as in Example 1, the surface roughness of the cam portion 1a after the remelting and hardening treatment was 11 μm (see FIG. 3), which was the same as in Examples 1 and 2.
It was far inferior to what it was.

Example 3 C: 3.7% by weight, Si: 2.2% by weight, Mn: 0.4
Weight%, P: 0.07% by weight, S: 0.03% by weight, C
A cam shaft 1 is roughly machined using alloyed cast iron having a composition of r: 0.07% by weight, Mg: 0.02% by weight, Fe, and the balance, and the surface of the cam portion 1a of the camshaft 1 is roughened to a surface roughness of 3.8 μm. Grinding was done. In other words, in this embodiment, the camshaft 1 is employed as the target component to be subjected to the remelting and hardening treatment. Next, after preheating the camshaft 1 to 300°C, a T is applied to the cam portion 1a.
At the same time as remelting was carried out using the IG arc torch 2, the remelting pool 5 formed on the surface of the cam portion 1a was stirred by electromagnetic waves using the TIG arc torch 2. The stirring conditions at this time were DUTY50%, frequency: 50Hz, and magnetic field strength 250 Gauss, and the remelting conditions were the same as those in Example 1.
It was the same.

In the case of this embodiment, during the remelting process by the TIG arc torch 2, a stirring action by electromagnetic waves is applied to the remelting pool 5 formed on the surface of the cam portion 1a.
Microvibrations are generated in the remelting pool 5, thereby reducing the surface tension of the remelting pool 5, promoting the generation of crystallized nuclei, and improving heat dissipation. As a result, the solidification of the remelting pool 5 is accelerated, and the occurrence of unevenness and shoulder sag in the formed hardened surface layer is suppressed.

In this example, the surface roughness of the cam part 1a after the remelting and hardening treatment was 3 to 5 μm (see Figure 4), and no shoulder sagging occurred at the end of the cam part 1a. Ta.

Example 4 The same camshaft 1 as in Example 3 above was used as the target part, and only the frequency of the electromagnetic waves was changed to 5 Hz, and remelting and hardening treatment was performed under the same remelting conditions as in Example 3. However, the surface roughness of the cam portion 1a after the remelting and hardening treatment is 6.
It was 5 to 8 μm (see FIG. 4), and no shoulder sag occurred at the end of the cam portion 1a.

In the case of each of the above embodiments, by preheating the Kamunyaft, which is the target part, to a predetermined temperature before performing the remelting hardening treatment, it is possible to prevent quench cracking due to high-density machining irradiation by TIG arc, etc. However, the temperature of the cam portion at this time is not necessarily constant, and constantly changes due to conduction of melting heat from other cam portions, radiation of retained heat held by the cam portion into the atmosphere, etc. On the other hand, the temperature of the cam part during the remelting hardening process depends on the depth of the remelting hardening layer,
It is well known that there are important factors that affect It becomes necessary to change other processing conditions depending on the temperature.

By the way, when the preheating temperature of the target processing part (in the case of the above example, the camshaft) was controlled within a certain range, and the temperature of the cam part at the remelting processing station was measured, the fifth
As shown in the figure, it has been found that the temperature of the cam portion at each remelting and hardening treatment station can be kept almost constant. Further, when the material of the cam part and the moving speed of the TIG arc torch are constant, the depth D of the remelted hardened layer is T
There is a fact that the current value I applied to the IG arc torch and the cam part temperature T are given by the following equation.

D=0.52I +1.74 By performing the remelting and hardening treatment, it becomes possible to make the depth of the remelting and hardening layer formed on each cam portion of the camshaft uniform.

Further, in each of the above embodiments, a TIG arc torch was used as the high-density energy irradiation device, but other methods such as a laser beam, plasma arc, electron beam, etc. may be used as the high-density energy irradiation device. You can also do that.

Further, in each of the above embodiments, the target component to be subjected to the remelting hardening treatment is a camshaft, but the method of the present invention is of course applicable to various other sliding members.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a remelting hardening treatment device used in Examples 1 and 2 of the present invention, and Fig. 2 shows a remelting pool formed on the surface of the cam portion of the camshaft using a TIG arc torch. FIG. 3 is a characteristic diagram showing the relationship between the vibration acceleration caused by the vibrator pen and the surface roughness of the remelted hardened layer in Examples 1 and 2 of the present invention, and FIG. , 4 is a characteristic diagram showing the relationship between the frequency of electromagnetic waves and the surface roughness of the remelting hardening layer. Figure 5 is a characteristic diagram showing the relationship between the frequency of electromagnetic waves and the surface roughness of the remelting hardening layer in each cam portion of the camshaft. A characteristic diagram showing changes in the temperature of the cam part, and FIG. 6 is a sectional view showing a remelting pool generated by a conventional method. 1... Target processing parts (camshaft) 2...
・・・・・・TIG arc torch 3・・・・・・Pie break pen 4・・・・・・Discharge arc 5・・・・・・Remelting pool −4+ R1,) ′″″L 〈 Low 106-

Claims (1)

[Claims] 1. A feature of the present invention is that when high-density energy is irradiated to the surface of the target part to re-melt and harden the part, minute vibrations are generated in the re-melt pool generated by the irradiation of the high-density energy. A method for manufacturing remelted and hardened parts.