JPH05331529A - Induction hardening jig - Google Patents

Abstract

PURPOSE:To decrease the thickness of an insulating coated layer and to improve high frequency induction heating efficiency by coating the surface of a hollow copper pipe for induction hardening to a steel material with a ceramic insulating layer composed of a crystallized glass. CONSTITUTION:For example, on the surface of the bar-like steel material P, the high frequency current is supplied while shifting a round shape part 11 composed of the hollow copper pipe 10 to the arrow mark direction, and after heating the surface of the steel material P by the inclusion current, the steel material is rapidly cooled with water and quenched. As the round shape copper pipe 10 itself is heated at high temp., cooling medium is passed through the hollow part and also, in order to prevent the breakage of the copper pipe caused by the contact with the steel material P, the crystallized glass is uniformly stuck on this surface, by a migration electro-deposition method and burnt at 800-1000 deg.C to form the insulating coated layer with the thin crystallized glass having uniform thickness. As this crystallized glass insulating coated layer is the ceramic layer, this layer has high heat resistance without erosion even at high temp., and as this layer can be formed to the extremely small thickness, the interval with the steel material P to be treated can be made to be extremely narrow and the excellent induction heating power efficiency is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction hardening jig for steel or the like, which dramatically improves the durability of its insulating coating and completely prevents product damage due to dielectric breakdown of the hardening jig. In addition, the insulating coating can be made extremely thin, which can significantly improve the induction heating efficiency.

[0002]

2. Description of the Related Art Induction hardening jigs have various shapes such as a circular shape and an L shape according to the shape of the product to be hardened (Japanese Utility Model Publication No. 59-193854, Japanese Utility Model Publication No. 60-94802). Basically, a copper tube (diameter 5 to 6 mm, wall thickness 1, 0 mm) is wrapped with asbestos to circulate a cooling liquid, and this asbestos is hardened with a varnish or the like and covered and dried. The typical shape structure will be described with reference to FIGS. 1 and 2. The induction hardening jig shown in FIG. 1 is a jig for induction hardening the surface of a cylindrical body such as a steel pipe. The copper pipe 10 is bent into a loop shape, and asbestos is wound around the circular portion 11. Is hardened with varnish to form the insulating coating layer 12. A high-frequency current with a voltage of 20 to 200 v is applied to the copper pipe 10, the steel pipe P to be quenched is inserted into the circular portion, and the quenching jig is moved in the longitudinal direction relative to the steel pipe at a constant speed ( (See Japanese Utility Model Laid-Open No. 58-36596),
The surface is heated to 850 to 900 ° C., water is applied thereto, and the mixture is water-cooled and quenched. Since a large current is passed through the copper tube 10, the copper tube itself generates heat to decompose the resin that is the binder material of the insulating coating layer 12 and lose the adhesion of the coated asbestos and the process of resin decomposition. Since the asbestos itself becomes brittle, when the steel pipe P (product) comes into contact with the coating layer 12, the coating layer in that portion is easily damaged and the copper pipe in that portion is exposed. When the copper pipe is exposed, the copper pipe 10 and the steel pipe P
And the surface of the steel pipe P is significantly damaged. In order to prevent this as much as possible, a cooling liquid is circulated through the copper pipe to cool it. However, it is still unavoidable that the insulating coating layer 12 is heated to a high temperature, so that the deterioration of the insulating coating layer 12 rapidly progresses. On the other hand, since the efficiency of induction heating is inversely proportional to the square of the gap between the surface of the copper pipe 10 and the surface of the steel pipe P, the thickness of the insulating coating layer is set to prevent the efficiency of induction heating from decreasing as much as possible. A few mm for the above asbestos impregnated with varnish
It is suppressed to the extent. Therefore, even a slight damage to the insulation coating layer will destroy the insulation and damage the product.
The maximum number of times that this type of conventional induction hardening jig can be used is actually only a few times. As a substitute for this, the insulation resistance is high, the insulation resistance is extremely thin, and the insulation characteristics and physical strength do not deteriorate even at extremely high temperatures, and the insulation is highly reliable. Must. Since there is no suitable one at this stage, conventional asbestos is hardened with varnish, etc., and is considered to have the highest insulation reliability and practicality after a short period of use. ing. By the way, it is well known theoretically that the ceramic insulating coating has excellent insulation resistance, heat resistance and abrasion resistance. However, since a normal ceramic insulator such as alumina has a high melting point, it is almost impossible to use it as an insulating coating for an induction hardening jig having copper as a base material. Therefore, it is conceivable to perform enamel coating as a material having an insulation property that is slightly inferior to that of alumina or the like, but that can be insulation-coated below the melting point of a base material such as copper. However, in the case of a normal enamel, the melting point of the base material such as copper is 850 to 900 ° C.
Although it is possible to form a coating layer by firing at, but because it remelts at this firing temperature, when used for things that require quenching at high temperatures such as steel, it should be as far as possible from the object to be heated Or it is necessary to use a enamel whose firing temperature is as high as possible. However, in the former case, the distance from the object to be heated becomes large, so that there is a drawback in that the energy utilization efficiency is deteriorated. On the other hand, in the latter case, when coating a enamel with high heat resistance and high heat resistance, There is a problem that the adhesiveness between the material and the enamel is reduced, peeling is likely to occur, and the base material is easily deformed during firing.

[0003]

DISCLOSURE OF THE INVENTION According to the present invention, the high insulation, heat resistance and wear resistance of a ceramic coating layer are used to dramatically improve the durability, reliability and induction heating efficiency of an induction heating jig. It was noted that it is extremely effective in improving this, and the above-mentioned problems in putting this to practical use, that is, insulation with heat resistance that can be used at high temperatures near the melting point of base materials such as copper pipes. It is an object of the present invention to provide an induction hardening jig in which a problem in forming a coating layer is solved and a high quality ceramic coating layer is formed to such an extent that it can be put to practical use.

[0004]

[Means for Solving the Problems] Means for solving the above problems are as follows. A crystallized glass coating layer having a melting temperature of 800 to 1000 ° C. is formed on the surface of a hollow base material formed into a predetermined shape. That is, it was formed (enameled coating).

[0005]

[Operation] When crystallized glass that is electrodeposited on the surface of a substrate such as a copper tube by the electrophoretic deposition method is baked at 800 to 1000 ° C, the electrodeposition layer made of crystallized glass melts and softens and flows. At the same time, crystallization progresses, the viscosity increases rapidly, and a crystallized glass layer (enameled coating) having a uniform and smooth surface state that is difficult to remelt is formed.
Since the crystallized glass layer after firing does not remelt at the firing temperature like a normal enamel due to crystallization and has excellent heat resistance, it is necessary to use it while continuously cooling like an induction hardening jig. It can be used up to near the melting point of crystallized glass. Therefore, even in the case where high quenching temperature is required such as steel, it can be used in a state close to the object to be heated, so that high induction heating efficiency can be obtained.

[0006]

[Example] 0.5% by weight of fine particles of crystallized glass (multi-component crystallized glass containing SiO ₂ , MgO, etc.) was added to isopropyl alcohol, and the dispersed slurry was used to form a copper tube 1 having a predetermined shape. The electrode plate 2 is immersed, the negative electrode is connected to the copper tube 1, and the positive electrode is connected to the electrode plate 2.
In this state, a current of 500 V and 0.01 A is applied to uniformly attach the crystallized glass to the surface of the copper tube 1 (see FIG. 3). This is baked at 950 ° C. for 20 minutes to form a continuous glass coating layer on the surface of the copper tube. At the same time as the crystallized glass melts, the viscosity of the crystallized glass rapidly increases and a crystallized glass coating layer having a uniform and smooth thickness is formed. The thickness of the crystallized glass layer is adjusted to 40 to 500 μm by adjusting the electrodeposition conditions. In this case, when the melting temperature of the crystallized glass is 800 ° C or lower, the remelting temperature is 80
Since it is relatively low at a little over 0 ° C, it is not practical. On the other hand, 10
At temperatures above 00 ° C, the melting point of the copper tube is close to 1085 ° C, which may cause deformation of the copper tube or peeling of the coating layer during firing. Therefore, even if crystallized glass with a higher melting temperature is used, it is practical. There is no advantage above. Further, if the thickness of the crystallized glass coating layer is 40 μm or less, sufficient insulation reliability cannot be obtained, and if it is thicker than 500 μm, the induction heating efficiency is simply reduced. The durability test results of the induction hardening jig having the crystallized glass insulating coating layer (enameled coating layer) of the present invention are as follows. Example 1: Induction hardening jig for sprocket, overall shape of jig; same as in the above example, melting temperature of crystallized glass: 950 ° C, induction heating temperature: 850-900 ° C, induction heating time: 1, 9 seconds Cooling time: 1, 5 seconds, attachment / detachment time: 20 seconds, conventional product, product of the present invention, thickness of insulating coating layer: 1600 μm, 180 μm, durability: 4 to 5 times, 10,000 times or more. Example 2: Induction hardening jig for long rails, overall shape of jig; L-shaped shape (for concrete shape, see Fig. 4
), Melting temperature of crystallized glass: 950 ° C., high frequency heating temperature: 850 to 900 ° C., high frequency heating time; moving at a speed of 1, 2 cm / min, long rail length: 2 m conventional product, present product, Thickness of insulating coating layer: 1800 μm, 200 μm, durability: 2-3 times, 5,000 times or more.

[0007]

[Effect] The object of the present invention is novel. Therefore, it is an excellent effect peculiar to the present invention that the heat resistance, wear resistance, and high insulation of the ceramic insulating coating can be put to practical use in an induction hardening jig by solving this novel problem. .
Since the ceramic insulation coating has extremely high wear resistance, even if the induction hardening jig comes into contact with the product to be hardened, its insulation breakdown does not occur easily, its reliability is high, and high frequency heating It can be done very safely. Moreover, the accuracy of the thickness of the ceramic insulation coating layer is extremely high (manufacturing error with respect to the planned value, ± 10 μm), so that the surface of the jig does not come into contact with the surface of the object to be heated (the product to be quenched). They can be designed and manufactured to be close to each other, which can significantly improve the efficiency of induction heating. Further, since the crystallized glass having a melting temperature of 1000 ° C. or less is used, it is possible to prevent the deformation of the base material and the peeling of the coating layer at the time of firing, and the remelting temperature of the crystallized glass becomes a little over 1000 ° C. Even if the surface of the coating layer is heated to near 1000 ° C. during high frequency heating, there is no risk of remelting, which makes it possible to repeatedly perform high frequency heating at a heating temperature of 1000 ° C. Since the durability is extremely excellent, the jig replacement frequency is almost equal to zero compared to the conventional product, so the jig replacement work and replacement time are almost equal to zero, improving work efficiency and efficiency. The running cost for the jig can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a conventional technique.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a schematic view of an electrodeposition apparatus for crystallized glass by the electrophoretic deposition method.

FIG. 4 is a perspective view showing a usage state of an induction hardening jig for an L-shaped rail.

[Explanation of symbols]

 1, 10 ... Copper tube 2 ... Electrode plate 11 ... Circular part 12 ... Insulation coating layer P ... Steel tube

Claims (1)

[Claims] 1. An induction hardening jig in which the surface of a hollow base material formed into a predetermined shape is coated with crystallized glass having a melting temperature of 800 to 1000 ° C.